Communication mode controlling method, mobile communication system, radio network controller, base station, and mobile communication terminal

ABSTRACT

A communication mode which should be set to a mobile communication terminal having a function of switching between an autonomous mode and a scheduling mode is determined based on an amount of interference in each of the communication modes in the cell of a base station, and/or communication characteristics of each of the communication modes, and a signal indicating an amount of communication data notified from the mobile communication terminal. The base station then notifies the determined communication mode to the mobile communication terminal.

RELATED APPLICATIONS

The present application is a continuation application which claims thebenefit under 35 U.S.C. §120 of application Ser. No. 11/408,173, filedApr. 21, 2006, which is a divisional application of application Ser. No.10/572,599, filed Mar. 20, 2006, (now U.S. Pat. No. 7,684,408, issuedMar. 23, 2010), and PCT/JP03/12552, filed Sep. 30, 2003, the disclosureof each is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a mobile communication system with CDMA(Code Division Multiple Access). More particularly, it relates to acommunication mode controlling method of, a mobile communication systemfor, and an RNC (Radio Network Controller) for controlling a switchingbetween communication modes according to the status of communicationsbetween a base station and a mobile communication terminal, the basestation, and the mobile communication terminal.

BACKGROUND OF THE INVENTION

Related art wireless multi-mode data communication methods include amethod (for example, refer to JP, 2002-369261,A) of switching between anautonomous mode in which data are transmitted and received autonomously,and a so-called scheduling mode in which data are transmitted andreceived according to requirements (i.e., scheduling) set for datatransmission and reception, such as a communication timing permitted bya base station, according to a data rate and so on.

According to this communication method, when packet data is transmittedat a low data rate of about 9.6 kbps between a base station and awireless device, for example, the transmission of the packet data iscarried out with the transmission mode being switched to the autonomousmode. On the contrary, when packet data is transmitted at a high datarate between a base station and a wireless device, the transmission ofthe packet data is carried out with the transmission mode being switchedto the scheduling mode.

In the scheduling mode, the base station transmits a signaling fornotifying scheduling frequently to the wireless device. For this reason,if there is not a certain or more amount of data for each transmission,the efficiency of data transmission is reduced with respect to thenumber of times that the signaling is performed.

In the above-mentioned related art data communication method, theabove-mentioned malfunction is removed by switching to the schedulingmode in the case of a high data rate at which the amount of data perunit time is large.

However, although the above-mentioned related art reference disclosesapplication of a switching to either the autonomous mode or thescheduling mode based on the amount of data to the above-mentionedrelated art data communication method, it does not disclose any processof switching between the autonomous mode and the scheduling mode underother communication conditions.

As the communication conditions which should be used as the referencefor switching between the communication modes, an amount of interference(referred to as a noise rise from here on), a delay time, or the like inthe base station can be provided, for example, by taking intoconsideration a process of demodulating an encoded signal, and a processof handling data of which real-time nature is required.

According to the invention disclosed by the above-mentioned related artreference, no due consideration is given to flexible communication modeswitching operations according to communication conditions, such as acommunication mode switching operation of making a wireless device whichcarries out data communications in which any delay time cannot bepermitted operate in the autonomous mode if possible, and making adevice which carries out communications in which a delay time can bepermitted operate in the schedule mode.

In uplink packet communications using a CDMA method, when interferencecaused by a transmission signal from a wireless device exceeds the limitof a noise rise in a base station, the base station cannot demodulatethe transmission signal.

This noise rise varies dependently upon interference by other cells,transmission from other wireless devices in the same cell, etc. For thisreason, it is necessary to sufficiently pay attention to the managementof the noise rise in the packet communications using a CDMA method.

When a margin for the noise rise is sufficiently secured as noise risemanagement, it is possible to use the autonomous mode even if the amountof data to be transmitted is large. In this case, the number of timesthat the signaling is performed can be reduced compared with the case ofthe schedule mode, and there is an advantage of being able to reduce thedelay time.

Thus, by appropriately dividing the margin for the noise rise resultingfrom various factors which vary according to the conditions of thecommunications traffic with respect to the noise rise margin of the basestation, efficient communications dependent upon changes in the noiserise can be carried out.

The present invention is made in order to solve the above-mentionedproblems, and it is therefore an object of the present invention toprovide a communication mode controlling method of making it possible tocarry out efficient data communications dependent upon changes in anoise rise caused by changes in the load of communications between abase station and a mobile communication terminal by switching betweencommunication modes appropriately in consideration of factors other thanthe amount of data.

It is another object of the present invention to provide a communicationmode controlling method of being able to divide a noise rise marginbetween an autonomous mode and a schedule mode according to QoS (Qualityof Service) by independently setting a threshold for switching betweentransmission modes to each terminal in consideration of QoS parameters,such as a delay time.

It is a further object of the present invention to provide a mobilecommunication system, an RNC, a base station, and a mobile communicationterminal, which carry out efficient data communications dependent uponchanges in a noise rise caused by a change in the load on communicationsusing the above-mentioned method.

DISCLOSURE OF THE INVENTION

In accordance with a communication mode controlling method of thepresent invention, in order for a mobile communication terminal toswitch between an autonomous mode in which the mobile communicationterminal autonomously carries out data communications with a basestation, and a scheduling mode in which the mobile communicationterminal carries out data communications with the base station at apermitted communication timing, a communication mode which should be setto the mobile communication terminal is determined based on an amount ofinterference in each of the communication modes in the cell of the basestation, and/or communication characteristics thereof, and a signalindicating the amount of communication data notified from the mobilecommunication terminal, and the base station notifies the determinedcommunication mode to the mobile communication terminal.

Therefore, the present invention offers an advantage of making itpossible to carry out efficient data communications according to achange in the noise rise which is caused by a change in the load ofcommunications between the base station and the mobile communicationterminal.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram schematically showing the structure of a mobilecommunication system in accordance with embodiment 1 of the presentinvention;

FIG. 2 is a diagram showing the configuration of channels for use in themobile communication system in accordance with embodiment 1;

FIGS. 3A and 3B are diagrams for explaining a communications mode inwireless multiplex data mode communications between a terminal and eachbase station in the mobile communication system in accordance withembodiment 1;

FIG. 4 is a diagram explaining the threshold of a transmission databuffer which is used as a reference for switching between communicationmodes of the mobile communication terminal according to embodiment 1;

FIG. 5 is a diagram showing a permissible margin for an amount ofinterference resulting from factors playing into uplink signalstransmitted to each base station in accordance with embodiment 1;

FIG. 6 is a diagram showing an example of a division of a noise risemargin between an autonomous mode and a scheduling mode when a pluralityof terminals use uplink packet communications in the cell of each basestation;

FIG. 7 is a diagram showing a case where the threshold for determiningwhether to switch between the communication modes of the transmissiondata buffer is set to be low in the example of FIG. 6;

FIG. 8 is a diagram showing an example of a division of the noise risemargin between the autonomous mode and the scheduling mode when thereare few terminals which use packet communications in the cell of eachbase station;

FIG. 9 is a diagram showing a case where the threshold for determiningwhether to switch between the communication modes of the transmissiondata buffer is set to be high in the example of FIG. 8;

FIG. 10 is a block diagram showing the internal structure of each basestation shown in FIG. 1;

FIG. 11 is a block diagram showing the internal structure of the mobilecommunication terminal shown in FIG. 1;

FIG. 12 is a block diagram showing the internal structure of an RNCshown in FIG. 1;

FIG. 13 is a diagram showing an example of a division of the noise risemargin of each base station when the RNC according to embodiment 1determines the threshold for switching between the transmission modes ofeach terminal according to a first method;

FIG. 14 is a diagram explaining a change in the threshold for switchingbetween the transmission modes according to the division of the noiserise margin shown in FIG. 13;

FIG. 15 is a diagram showing a changing sequence in a case of changingthe threshold of the transmission data buffer using the first method inthe mobile communication system according to embodiment 1;

FIG. 16 is a flow chart for explaining a process of step ST9 in FIG. 15in detail;

FIG. 17 is a diagram showing an example of a division of the noise risemargin of each base station when the RNC according to embodiment 1determines the threshold for switching between the transmission modes ofeach terminal according to a second method;

FIG. 18 is a diagram explaining a change in the threshold for switchingbetween the transmission modes according to the division of the noiserise margin shown in FIG. 17;

FIG. 19 is a diagram showing a changing sequence in a case of changingthe threshold of the transmission data buffer using the second method inthe mobile communication system according to embodiment 1;

FIG. 20 is a flow chart for explaining a process of step ST9 b in FIG.19 in detail;

FIG. 21 is a diagram showing an example of a division of the noise risemargin of a base station according to embodiment 1 when the base stationdetermines the threshold for switching between the transmission modes ofeach terminal according to a third method;

FIG. 22 is a diagram showing a changing sequence in a case of changingthe threshold of the transmission data buffer using the third method inthe mobile communication system according to embodiment 1;

FIG. 23 is a flow chart for explaining a process of step ST3 d in FIG.22 in detail;

FIG. 24 is a flow chart showing the operation of the mobilecommunication system in a case where the first method is applied to astructure in which the mobile communication terminal switches betweenthe transmission modes according to a command from a base station;

FIG. 25 is a flow chart showing the operation of the mobilecommunication system in a case where the second method is applied to thestructure in which the mobile communication terminal switches betweenthe transmission modes according to a command from a base station; and

FIG. 26 is a flow chart showing the operation of the mobilecommunication system in a case where the third method is applied to thestructure in which the mobile communication terminal switches betweenthe transmission modes according to a command from a base station.

PREFERRED EMBODIMENTS OF THE INVENTION

In order to explain the invention in greater detail, the preferredembodiments of the invention will be explained below with reference tothe accompanying figures.

Embodiment 1

FIG. 1 is a diagram schematically showing the structure of a mobilecommunication system in accordance with embodiment 1 of the presentinvention. The mobile communication system 1 is provided with a mobilecommunication terminal 2 which the user uses, an RNC (Radio NetworkController) 3, and base stations 4 a and 4 b. The RNC 3 is disposedbetween a construction disposed on a side of a network, such as a publicnetwork, and the base stations 4 a and 4 b, and relays packetcommunications between them.

Thus, the system 1 is so constructed that the RNC 3 controls the two ormore base stations 4 a and 4 b for the side of the network. As a result,in the system 1, a radio link which is called a soft handover can beestablished among the two or more base stations 4 a and 4 b for oneterminal 2.

When the mobile communication system 1 is implemented using a W-CDMA(Wideband-Code Division Multiple Access) method, the mobilecommunication terminal 2 can be called UE (User Equipment), the RNC 3can be called RNC (Radio Network Controller), and each of the basestations 4 a and 4 b can be called Node-B.

Especially, in high-speed uplink packet communications, a specific basestation may take on the task of performing scheduling about datacommunications with a certain terminal. In this case, the specific basestation may be called a serving cell for the sake of a distinction fromother base stations. A base station is also called, as a whole, a cellincluding a specific area in which it carries out communicationsprocessing. In the later explanation, these terms will be used as deemedappropriate.

FIG. 2 is a diagram showing, as an example, the configuration ofchannels for use in the mobile communication system in accordance withembodiment 1, and shows the configuration of channels in a wirelesssection between each of the base stations 4 a and 4 b and the terminal 2of the W-CDMA system.

The channels of this figure are shown as an example, and the channelsfor use in the mobile communication system are not limited to the shownchannels. Actually, two or more control channels can be used so thatthey can share a single channel.

First, downlink channels from each of the base stations 4 a and 4 b tothe terminal 2 will be explained. The downlink channels include a CPICH(Common Pilot Channel) via which each of the base stations notifies areference for all timings to formation parts disposed in the cell, and aP-CCPCH (Primary-Common Control Physical Channel) which is a physicalchannel for BCH (Broadcast channel), and via which each of the basestations notifies broadcast information other than the reference to theterminal 2.

The downlink channels include, as channels for use in uplink packetcommunications, a DL-SACCH (Downlink Scheduling Assignment ControlChannel) via which each of the base stations notifies an assignmentposition provided by a scheduler for transmission of controlinformation, and a DL-ACK/NACK-CCH (Downlink AckINack Control Channel)via which each of the base stations 4 a and 4 b notifies the success orfailure of reception of packets. Furthermore, there is an FACH (ForwardAccess Channel) as a downlink common channel.

Next, uplink channels from the terminal 2 to each of the base stations 4a and 4 b will be explained. The uplink channels include, as channelsfor use in uplink packet communications, a UL-SICCH (Uplink SchedulingInformation Control Channel) via which the terminal 2 notifies existenceof transmission data to each of the base stations, a UL-TFRI-CCH (UplinkTFRI Control Channel) via which the terminal 2 notifies a modulationmethod, an encoding rate, and so on which are selected thereby to eachof the base stations 4 a and 4 b, and an EUDTCH (Enhanced UplinkDedicated Transport Channel) via which the terminal 2 transmits userdata in uplink packet communications. Furthermore, there is an RACH(Random Access Channel) as an uplink common channel.

In addition, as a channel set for both the uplink and downlinkcommunications, there is a DPCH (Dedicated Physical channel) which isset up separately for communications with a specific terminal, and whichis used for communications of audio data, data, etc., or signaling by anupper layer. The DPCH can be separately referred to as a DPDCH(Dedicated Physical Data channel) for transmitting data and a DPCCH(Dedicated Physical Control channel) for transmitting a bit associatedwith control.

FIGS. 3A and 3B are diagrams for explaining a communications mode inwireless multi-data mode communications between the terminal and eachbase station in the mobile communication system in accordance withembodiment 1. As shown in FIG. 3A, when data transmission processing iscarried out in an autonomous mode, each of the base stations (Node-B) 4a and 4 b specifies a range of permissible rates first for the terminal(UE) 2 in advance. At this time, the UE transmits data to each Node-B atan arbitrary time and at a rate which falls within the range ofpermissible rates. When receiving data from the UE, each Node-Btransmits a response signal (ACK/NACK) to the UE.

In the autonomous mode, it is not necessary to necessarily specify therange of permissible rates for every packet transmission, and to-and-frocommunications processing including transmission of data and a responseto the data transmission only have to be carried out basically.

For this reason, the autonomous mode has an advantage of having smallwastes in signaling and a short delay time because the UE can carry outtransmission of data freely when desiring to transmit the data.

On the contrary, a disadvantage of the autonomous mode is that a noiserise margin required for the amount of interference which will occurwhen transmission of data is carried out must be always secured so thatthe UE can transmit the data at an arbitrary time.

On the other hand, in the data transmission processing in the schedulingmode, the UE transmits information, such as information indicating thestatus of a UE buffer, to each Node-B, as shown in FIG. 3B. Whenreceiving the information, each Node-B carries out scheduling fortransmission of uplink packets to two or more UEs, and also assigns atime period (or a subframe) during which a UE is permitted to carry outtransmission of data and a transmission rate to the UE which ispermitted to transmit data by the Node-B. The UE transmits packets toeach Node-B according to the assigned time period and transmission rate,and receives a response signal from each Node-B.

The scheduling mode has an advantage that it is not necessary to set upan excessive noise rise margin since any UE to which a time period and atransmission rate are not assigned by the scheduler does not carry outtransmission of data.

On the other hand, the scheduling mode has a disadvantage that it isnecessary to carry out two-time to-and-fro communications processingincluding at least communications processing required for thescheduling, and processing for transmitting data body, and therefore adelay time occurs inevitably.

In addition, since a signaling for notifying the existence oftransmission data in the UE to each Node-B must be performed in advance,the efficiency will be worsened when the amount of transmission data issmall with respect to the number of times that the signaling is carriedout.

In the autonomous mode, each base station does not specify thetransmission timing and the terminal itself determines the transmissiontiming autonomously. On the other hand, in the scheduling mode, eachbase station specifies and notifies the transmission timing to theterminal, and the terminal transmits data to each base station accordingto the transmission timing.

Furthermore, even in the scheduling mode, each base station may specifythe data rate. For example, in the autonomous mode each base stationspecifies and notifies the transmission data rate for data transmissionto the terminal, whereas even in the scheduling mode each base stationmay specify and notify the transmission timing and transmission datarate to the terminal so as to control data transmission by the terminal.

FIG. 4 is a diagram explaining a threshold (threshold) of thetransmission data buffer, which is used as a reference to make themobile communication terminal in accordance with embodiment 1 switchbetween the communication modes. The mobile communication terminal 2operates in the autonomous mode when it is placed in a state wheretransmission data having an amount equal to or smaller than thethreshold of the transmission data buffer remains therein. On the otherhand, when transmission data having an amount exceeding theabove-mentioned threshold remains in the transmission data buffer, themobile communication terminal 2 switches to the scheduling mode and thenoperates.

Thus, the terminal 2 switches between the autonomous mode and thescheduling mode based on the threshold associated with the storageamount of transmission data in the transmission data buffer. Thedetermination of this threshold will be mentioned later.

FIG. 5 is a diagram showing a permissible margin for an amount ofinterference (referred to as a noise rise from here on) resulting fromfactors playing in uplink signals transmitted to each base station inaccordance with embodiment 1. In general, in a CDMA system, although acertain amount of interference is permitted for a received encodedsignal, if the amount of interference exceeds the permissible limit ofthe noise rise, the amount of interference becomes larger than themagnitude of the signal and it is therefore impossible to decode theabove-mentioned signal correctly even if back spreading is performed onthe signal.

For this reason, it is important how the noise rise is controlled sothat the ideal amount of interference falls within a range from a zerostate (i.e., the bottom of the noise rise) to the permissible limit ofinterference at which any received signal can be decoded in order tosecure the capacity of each base station (i.e., the number of terminalswhich can be accommodated by each base station).

As shown in the figure, a noise rise which results from transmission inthe scheduling mode or transmission in the autonomous mode and which isincluded in noise rises which occur at each base station's end can becontrolled so that it falls within a margin in the scheduling mode and amargin in the autonomous mode by switching between these transmissionmodes properly in the uplink packet communications.

On the other hand, a noise rise which results from factors other thanthe scheduling mode and autonomous mode cannot be controlled so that itfalls within the margin in the scheduling mode and the margin in theautonomous mode.

Factors responsible for such interference in each base station are, forexample, own cell interference which is approximated by the total powerof desired signals from terminals staying in the own cell, other-cellinterference which is caused by needless reception of signals fromterminals which are staying in the cover areas of other base stations,and thermal noise which is caused by a receiver disposed in each basestation.

Therefore, whether to efficiently use the radio resources for the uplinkpacket communications depends upon how the range of the noise rise isadjusted by controlling the margin in the scheduling mode and the marginin the autonomous mode.

FIG. 6 is a diagram showing an example of a division of the noise risemargin (i.e., the permissible amount of interference) of each basestation between the autonomous mode and the scheduling mode when aplurality of terminals use the uplink packet communications in the cellof each base station. The illustrated example shows a case where alarger number of terminals are accommodated in the cell of each basestation as compared with a below-mentioned case of FIG. 8.

As will be mentioned later in detail, a margin of a fixed range which isdetermined by the RNC 3 in consideration of the QoS parameters, such asa delay time, is set, as a controllable noise rise margin as shown inFIG. 5, to each base station in accordance with embodiment 1. When thepermissible margin for the noise rise which results from the autonomousmode is acquired from this noise rise margin, a larger noise rise marginonly has to be set per terminal in the cell.

At this time, since the whole noise rise margin is set to have a fixedrange, a permissible margin (i.e., a diagonally shaded area) for thenoise rise resulting from the scheduling mode must be reduced by onlythe increase in the noise rise margin per terminal, as shown in FIG. 6(a).

Therefore, in the case shown in FIG. 6( a), when the number of terminalsin the cell which communicate with each base station in the schedulingmode increases, there is a possibility that the noise rise resultingfrom this increase cannot be controlled so that it falls within thepermissible margin.

On the contrary, when the noise rise margin per terminal in the cell forthe uplink packet communications is set to be smaller, a largerpermissible margin (i.e., a diagonally shaded area) for the noise riseresulting from the scheduling mode can be secured in each base station,as shown in FIG. 6( b).

In other words, when a large number of terminals which communicate witheach base station in the scheduling mode exist within the cell, it isnecessary to reduce the permissible margin per terminal for the noiserise resulting from the autonomous mode as much as possible.

In the uplink packet communications, as the amount of data which aterminal transmits to each base station at a time becomes less, thetransmission rate decreases. At this time, since the terminal lowers thetransmission power required for the data transmission, the noise rise inthe signal received by each base station also decreases.

Therefore, as shown in FIG. 6( b), in order to reduce the permissiblemargin per terminal for the noise rise resulting from the autonomousmode as much as possible, what is necessary is just to reduce the noiserise itself resulting from the autonomous mode, that is, to cause theterminal to carry out communications at a low data rate in theautonomous mode.

To be more specific, it is desirable to, when there are many terminalsaccommodated in the cell, set the threshold used for determining whetherto switch between the communication modes of the transmission databuffer of each terminal to be lower, and to, when the amount oftransmission data exceeds a small-amount range at low data rates, switchfrom the autonomous mode to the scheduling mode, as shown in FIG. 7.

Then, as shown in FIG. 8, a case where a small number of terminals usinguplink packet communications exist in the cell (in the example of FIG.8, two terminals exist in the cell as compared with the case of FIG. 6where seven terminals exist in the cell) will be described as anexample. In this case, even if a large noise rise margin per terminal isset in each base station, as shown in FIG. 8( a), a sufficientpermissible margin (i.e., a diagonally shaded area) for the noise riseresulting from the scheduling mode can be secured in each base station.

As shown in FIG. 8( b), even if a smaller noise rise margin per terminalis set in each base station, there is not much difference between thepermissible margin for the noise rise resulting from the scheduling modeand that in the case of FIG. 8( a).

In other words, when the number of terminals accommodated in the cell ofa base station is small, each of the terminals can carry outcommunications with the base station at a higher data rate even in theautonomous mode as compared with the case of FIG. 6.

To be more specific, when the number of terminals accommodated in thecell is small, the threshold used for determining whether to switchbetween the communication modes of the transmission data buffer of eachterminal is set to be large so that a higher data rate can be permittedand therefore a larger amount of data can be handled even in theautonomous mode, as shown in FIG. 9.

As can be seen from the above description, it is clear that in order toimplement reduced-interference high-quality communications it isdesirable to properly change the above-mentioned threshold of thetransmission data buffer of each terminal according to the trafficsituation in the communications between each terminal and each basestation, for example, the number of the terminals which operate in thescheduling mode within the cell and the operating states of theterminals, and schedules according to which the terminals operation inthe autonomous mode and the operating states of the terminals.

Taking into consideration that the system has a communicationcharacteristic of having a small transmission delay time in theautonomous mode, it is desirable to, when the permissible margin fordivision of the noise rise is enough, cause a terminal which makes asevere request about delay times to communicate with each base stationin the autonomous mode if possible.

FIG. 10 is a block diagram showing the internal structure of each basestation shown in FIG. 1. Hereafter, the fundamental operation of eachbase station will be explained with reference to this diagram. In FIG.10, in order to prevent redundant description, simplified names aregiven to formation parts which will be mentioned later, and the sameformation parts as previously mentioned are designated by the samereference numerals.

First, processing common to both general CDMA modulation anddemodulation will be explained.

A transmitting operation will be explained first. A modulating unit 5disposed in each of the base stations 4 a and 4 b multiplies signalsreceived via channels (P-CCPCH, downlink DPDCH, FACH, CPICH, DL-SACCH,DL-ACK/NACK-CCH, downlink DPCCH, etc.) by a channelization codegenerated by a downlink channelization code generator 6, and thenmultiplexes these signals into a signal.

The modulating unit 5 then multiplies the signal into which thosesignals associated with the channels are multiplexed by a scramblingcode generated by a downlink scrambling code generator 7, and performsspectrum spread processing on the signal which is multiplied by thescrambling code.

A baseband signal which is a signal associated with each of the channelsmultiplexed by the modulating unit 5 is outputted to a frequencyconverting unit 8. The frequency converting unit 8 increases thefrequency of the above-mentioned baseband signal to a carrier frequency,and outputs it to a power amplifying unit 9. The power amplifying unit 9amplifies the signal furnished thereto from the frequency convertingunit 8 using an internal power amplifier so that the signal has desiredpower. The signal amplified by the power amplifying unit 9 istransmitted to the terminal 2 via an antenna 10.

When receiving a clock signal which serves as a reference from a timingmanagement unit 26, a pilot signal generating unit 27 assigns a pilotsignal which the terminal 2 uses as a reference for demodulationprocessing to CPICH, and sends out it to the whole of the cell.

Next, a receiving operation will be explained. A weak signal receivedvia the antenna 10 is furnished to a low noise amplifier unit 11. Afteramplifying this signal, this low noise amplifier unit 11 outputs theamplified signal to a frequency converting unit 12. The frequencyconverting unit 12 reduces the frequency of the signal furnished theretofrom the low noise amplifier unit 11 to the frequency of theabove-mentioned baseband signal.

A back spreading unit 15 multiplies the baseband signal whose frequencyis frequency-converted by the frequency converting unit 12 by ascrambling code generated by an uplink scrambling code generator 13 andperforms back spreading processing on the multiplication result so as toextract a signal component associated with each terminal. A demodulatingunit 30 demultiplexes the signal on which the back spreading processingis performed and which is furnished thereto from the back spreading unit15 into signals respectively associated with channels using achannelization code generated by an uplink channelization code generator14.

Then, a process of acquiring the power of a signal and the power ofinterference will be explained.

First, a desired wave power measurement unit 16 acquires the power of adesired wave from a pilot signal associated with DPCCH from the backspreading unit 15. On the other hand, the low noise amplifier unit 11acquires the total reception power of the received signal in which thedesired wave and a noise coexist via the antenna 10.

An interference wave power measurement unit 17 acquires the power of aninterference wave which is a noise component by subtracting the power ofthe desired wave acquired by the desired wave power measurement unit 16from the above-mentioned total reception power furnished thereto via thelow noise amplifier unit 11, frequency converting unit 12, and backspreading unit 15.

Then, the power of the desired wave and that of the interference waveare sent from the measurement units 16 and 17 to an uplink packettransmission management unit 24, respectively. Thus, the uplink packettransmission management unit 24 acquires the power of the desired signalfrom each terminal staying in the own cell.

The uplink packet transmission management unit (i.e., a communicationmanagement unit) 24 also acquires interference components (i.e., noiserises) which are caused by own cell interference in the uplink packetcommunications, other-cell interference, and thermal noise from the RNC3.

Since a code for interference (other-cell interference and thermalnoise) other than the own cell interference is unknown, no signal can beseparated from any noise. For this reason, the uplink packettransmission management unit 24 acquires an interference component otherthan the own cell interference component from the RNC 3 as the power ofthe interference in which the other-cell interference and the noisecaused by thermal noise coexist. Although the other-cell interferenceand the thermal noise coexist in the above-mentioned interferencecomponent and cannot be distinguished from each other, it is notnecessary to distinguish especially between them in the process ofcontrolling the amount of interference.

Then, the uplink packet transmission management unit 24 subtracts thepermissible margin associated with the own cell interference and thepermissible margin associated with the interference in which theother-cell interference and the noise caused by thermal noise coexistfrom a permissible margin of a fixed range which is based on a jammingmargin so as to acquire the noise rise margin which is controllable inthe uplink packet communications.

The jamming margin is an index indicating a maximum permissibleaccommodation capacity (i.e., the number of terminals which can beaccommodated in the cell), and is defined as the ratio J/S of the signalpower S to the power J of interference components. The accommodationcapacity of the cell (i.e., the number of terminals which can beaccommodated in the cell) can be acquired from the above-mentionedjamming margin.

The above-mentioned accommodation capacity shows the number of terminalswhich can be accommodated in the cell of the base station in questionexcept for terminals which are a target for communications of a certainbase station at the current time.

The above-mentioned jamming margin is computed by a below-mentionedradio resources management unit disposed in the RNC 3 according to, forexample, the following relational equation.

First, when the power of a signal received by the base station is S (W)and the transfer rate at which communication data is transmitted is R(bit/second), the power Eb per 1 bit of the signal is expressed by thefollowing equation (1):Eb=S/R  (1)where S is the power of the signal from the mobile communicationterminal 2 which is received by the base station. It is further assumedthat the base station receives the signal at a uniform level using ahigh-speed power control function (i.e., an inner loop) which is basedon a TPC command of CDMA. In the W-CDMA, S can be acquired from theintensity of the pilot signal, and R can be acquired using a commandsuch as TFCI.

Next, the power I₀ (W) of the interference components from otherterminals staying in the cell of the base station can be expressed by,for example, the following equation (2):

$\begin{matrix}{I_{0} = {{\sum\limits_{i = 1}^{N - 1}\frac{Si}{Ri}} = \frac{\left( {N - 1} \right)S}{R}}} & (2)\end{matrix}$where N (number) is a maximum number of terminals which can beaccommodated in the cell, assuming that the local terminal is excludedfrom the terminals. Si is the power of a signal which the base stationreceives from a terminal 2 which is one of the first to (N−1)-thterminals, and the suffix i is a positive integer ranging from 1 to(N−1), and Ri is the transfer rate (bit/second) at which the basestation receives communication data from a terminal 2 which is one ofthe first to (N−1)-th terminals.

As a result, I₀ is expressed by the sum of the signal powers of theother terminals, the number of these terminals being equal to (themaximum number N−1), In the above-mentioned equation (2), it is assumedthat the signal power and transfer rate of each terminal 2 are equal andare given by S and R, respectively.

Since it is inconvenient to distinguish noise for every band width, theinterference components caused by the other-cell interference and thethermal noise are processed as an average noise power spectral densityNo (W) which is converted into noise energy per Hz withoutdistinguishing noise for every band width as mentioned above.

When the spectrum band of a spread spectrum signal is W (Hz) and thepower of narrowband disturbance noise is J (W), (No+Io) which is thenoise rises (i.e., the amount of interference) caused by the own cellinterference, the other-cell interference, and the thermal noise can beexpressed by the following equation:No+Io=J/W  (3)where SIR (Signal-to-Interference Ratio) can be acquired from Eb/(No+Io)which is the ratio of the energy Eb per 1 bit of the signal, and the sumof the noise rises caused by the thermal noise, the other-cellinterference, and the own cell interference.

Using the above-mentioned equations (1) and (3), SIR can be expressed bythe following equation (4):Eb/(No+Io)=S·W/(J−R)  (4)

Transformation of the above-mentioned equation (4) to obtain the limitof the jamming margin (jamming margin) J/S at which demodulation can beperformed in CDMA yields the following equation (5):J/S=(W/R)/{Eb/(No+Io)}  (5)

The RNC 3 determines the permissible margin having a fixed range inwhich a margin associated with the interference which is determined inconsideration of the QoS parameters, such as the operating states ofother cells other than target base stations which the RNC itselfmanages, the traffic conditions of the cells of the target basestations, and delay times, is incorporated into the above-mentionedjamming margin (i.e., acquires a margin by subtracting the marginassociated with the interference which is determined in consideration ofthe QoS parameters, such as the operating states of other cells otherthan the target base stations, the traffic conditions of the cells ofthe target base stations, and delay times from the jamming margin) andnotifies the determined permissible margin to the target base stations.

Each target base station performs noise rise control by performing aswitching between the communication modes so that the noise rises arecontrolled to within the limit of the above-mentioned permissible marginnotified from the RNC 3.

By doing in this way, each target base station can prevent the amount ofinterference in the received signal from exceeding the jamming marginwhich is the limit within which the signal can be demodulated under theinfluence of the operating states of other cells other than the localstation upon the communications by the local station even if each targetbase station performs the above-mentioned control. The details of thisprocessing will be explained later.

The uplink packet transmission management unit 24 disposed in eachtarget base station uses a remaining margin which is obtained bysubtracting the permissible margin (i.e., the uncontrollable marginshown in FIG. 5) for the noise rises caused by the thermal noise, theother-cell interference, and the own cell interference from theabove-mentioned permissible margin of a fixed range as the controllablenoise rise margin shown in FIG. 5.

Assuming that the power of a signal from any of all the terminalsstaying in the own cell is a constant value S, and the interferencepower J (W) results from the interference from other terminals otherthan the target terminal, the interference power J can be expressed bythe following equation (6):J=(N−1)S  (6)

The following equation (7) can be driven from the above-mentionedequations (5) and (6).(N−1)=(W/R)/{Eb/(No+Io)}  (7)

In the above-mentioned equation (7), (N−1) is a maximum number ofterminals, excluding the target terminal, which can be accommodated inthe own cell. It is clear that as the transfer rate R of communicationdata is made to increase, the jamming margin decreases from the valuegiven by the above-mentioned equation (5), and the capacity of terminalsin the own cell decreases from the value given by the above-mentionedequation (7).

It is further clear that in a case where SIR between the target terminaland each base station increases, the jamming margin decreases from thevalue given by the above-mentioned equation (5) even when each basestation makes a request of the target terminal for larger transmissionpower in order to secure a predetermined BER (bit error rate), forexample.

Returning to the explanation about the operation of each base station, achannel quality measurement unit 18 computes a signal-to-interferencepower ratio (SIR) using the power of the desired wave and that of theinterference wave furnished from the desired wave power measurement unit16 and interference wave power measurement unit 17, respectively, andthe power of the interference components caused by the own cellinterference, the other-cell interference, and the thermal noise, whichis acquired from the RNC 3, and outputs the computedsignal-to-interference power ratio to a quality target comparing unit19.

In the W-CDMA system, control of the transmission power of each terminalis carried out based on a target SIR value which is called an outerloop. This target SIR value is preset to the quality target comparingunit 19.

A decoding unit 22 disposed in each base station counts a block errorrate (BLER) from CRC (Cyclic Redundancy Check) errors in communicationswith a target terminal, and, if a required BLER is no longer filled,performs a change in settings, e.g., increases the target SIR valuepreset to the quality target comparing unit 19. This operation is calledouter loop power control.

On the other hand, the quality target comparing unit 19 compares thesignal-to-interference power ratio (SIR) computed by the channel qualitymeasurement unit 18 with the target signal-to-interference ratio (i.e.,the target SIR value), and notifies the result of the comparison to aTPC generating unit 20.

When determining from the above-mentioned comparison result that thepower of the desired signal in the received signal is smaller than thatof the target signal, the TPC generating unit 20 assigns a command toincrease the transmission power, as a TPC (Transmission Power Command)which is called an inner loop, to the downlink DPCCH, and outputs thecommand to the modulating unit 5.

The signal transmitted, via the downlink DPCCH, from the TPC generatingunit 20 is transmitted to the terminal 2 via the modulating unit 5,frequency converting unit 8, power amplifying unit 9, and antenna 10, asmentioned above.

On the contrary, when determining from the above-mentioned comparisonresult that the power of the desired signal in the received signal islarger than that of the target signal, the TPC generating unit 20assigns a command to decrease the transmission power to the downlinkDPCCH, and outputs the command to the modulating unit 5. The subsequentprocessings are performed in the same way. Such the power control iscalled inner loop power control.

In the CDMA system, strengthening the intensity of a certain signal isexactly causing interference to other signals. For this reason, eachbase station controls the power of a signal which it transmits orreceives by performing the above-mentioned processing so that the powerfalls within a required and sufficient range of signal power.

Next, a scheme required for the uplink packet communications will beexplained.

First, the operation in the autonomous mode will be explained.

In the operation in the autonomous mode, each of the base stations 4 aand 4 b transmits information about a transmission permissible margin tothe terminal 2 using DL-SACCH or a similar downlink signaling channel inadvance. The transmission permissible margin is information forspecifying communication conditions required for each base station todemodulate a signal which the terminal 2 has transmitted, via uplinkpacket communications, to each base station in the autonomous mode. Forexample, the transmission permissible margin is a maximum permissibledata rate.

After that, when receiving a signal from the terminal 2, thedemodulating unit 30 demultiplexes the received signal into signalsassociated with channels according to the above-mentioned operation ofthe receive side.

A TFRI receiving unit 21 receives a signal associated with UL-TFRI-CCH,in which TFRI (Transport Format Resource Indicator) including modulationparameters selected by the terminal 2 and a transport format are set,among the signals associated with channels into which the receivedsignal is demultiplexed by the demodulating unit 30.

The TFRI receiving unit 21 then extracts demodulation parameters forEUDTCH from the signal associated with UL-TFRI-CCH, and sets them to thedemodulating unit 30 and decoding unit 22. The demodulating unit 30demodulates the received signal to generate the data body transmitted,via EUDTCH, from the terminal 2 using the demodulation parameters forEUDTCH, and outputs the data body to the decoding unit 22. The decodingunit 22 decodes the data body transmitted, via EUDTCH, from the terminal2 using the demodulation parameters for EUDTCH.

A response signal generating unit 23 determines whether the packet datatransmitted from the terminal 2 has been correctly received by each ofthe base stations 4 a and 4 b using the decoded result obtained by thedecoding unit 22.

When determining that the packet data has been correctly received byeach of the base stations 4 a and 4 b, the response signal generatingunit 23 generates ACK for notifying that each of the base stations hassucceeded in the reception of the packet data, assigns it toDL-ACK/NACK-CCH, and sends it to the terminal 2 according to theabove-mentioned sending operation. On the contrary, when determiningthat the packet data from the terminal 2 has an error, the responsesignal generating unit 23 generates NACK for notifying that thereception of the packet data has failed, and similarly sends it to theterminal 2.

Next, the operation in the scheduling mode will be explained.

In the operation in the scheduling mode, a transmission buffer amountreceiving unit 31 receives a signal associated with UL-SICH from thedemodulating unit 30 so as to acquire information about the transmissiondata in the terminal 2 placed in the scheduling mode, and notifies it tothe uplink packet transmission management unit 24.

The uplink packet transmission management unit 24 of each base stationacquires a timing for subframes from the timing management unit 26, andsynthetically determines the amount of data which remain in thetransmission data buffer of each terminal staying in the own cell ofeach base station, the transmission power margin of each terminal, etc.,so as to determine a transmission timing for packets.

The uplink packet transmission management unit 24 notifies thedetermined transmission timing for packets to a transmitting rate/timingspecification information transmitting unit 25. The transmittingrate/timing specification information transmitting unit 25 assignssubframes for which transmission is permitted and the transmission rateto DL-SACCH, and transmits them to the above-mentioned terminal 2according to the above-mentioned sending operation.

After that, when receiving a signal from the above-mentioned terminal 2,the demodulating unit 30 demultiplexes the received signal into signalsassociated with channels according to the above-mentioned operation ofthe receive side.

The TFRI receiving unit 21 receives a signal associated withUL-TFRI-CCH, in which TFRI for subframes for which a permission fortransmission is provided by the above-mentioned terminal 2 is set, amongthe signals associated with channels into which the received signal isdemultiplexed by the demodulating unit 30.

The TFRI receiving unit 21 then extracts demodulation parameters forEUDTCH from the signal associated with UL-TFRI-CCH, and sets them to thedemodulating unit 30 and decoding unit 22. The demodulating unit 30demodulates the received signal to generate the data body transmitted,via EUDTCH, from the terminal 2 using the demodulation parameters forEUDTCH, and outputs the data body to the decoding unit 22. The decodingunit 22 decodes the data body transmitted, via EUDTCH, from the terminal2 using the demodulation parameters for EUDTCH.

When a packet transmitted from the above-mentioned terminal 2 has beencorrectly received by each base station, the response signal generatingunit 23 of each base station generates ACK and assigns this toDL-ACK/NACK-CCH, and sends ACK to the terminal 2, whereas whendetermining that the packet has an error, the response signal generatingunit generates NACK and assigns this to DL-ACK/NACK-CCH, and sends NACKto the terminal 2, as mentioned above.

Next, a scheme for performing a signaling to change the threshold usedfor switching between the communication modes of the transmission databuffer will be explained.

First, when notifying (or signaling) a change in the above-mentionedthreshold to each terminal 2 staying in the own cell of a base stationall at once, the uplink packet transmission management unit 24 of thebase station determines the change in consideration of the trafficconditions of the own cell etc., and notifies the change to the RNC 3.

The RNC 3 takes into consideration the operating states, etc. of otherbase stations other than the base station which has provided thenotification, generates information about the above-mentioned threshold(i.e., information indicating that the threshold should be changed towhat value, etc.), inserts it into broadcast information, and thentransmits the broadcast information to the base station in question.

A broadcast information transmitting unit 28 disposed in the basestation receives the broadcast information into which the informationabout the above-mentioned threshold is inserted from the RNC 3, assignsthe broadcast information to P-CCPCH (BCH), and transmits it to eachterminal 2 according to the above-mentioned sending operation. Theabove-mentioned broadcast information can be assigned to another channelin some rare cases.

When setting the above-mentioned changed threshold to each individualterminal 2, the uplink packet transmission management unit 24 disposedin the base station which accommodates the terminal 2 in question in thecell thereof determines the change in the threshold in consideration ofthe traffic conditions etc. of the communications with the terminal 2 inquestion, and notifies the change to the RNC 3.

The RNC 3 takes into consideration the operating states, etc. of otherbase stations other than the base station which has provided thenotification, generates information about the above-mentioned threshold(i.e., information indicating that the threshold should be changed towhat value, etc.), assigns it, as a message, to the dedicated channel,and transmits it to the base station in question.

When receiving the message about the above-mentioned threshold via thededicated channel, a downlink dedicated channel transmission unit 29disposed in the base station assigns the message to downlink DPDCH(DPCH), and transmits it to the terminal 2 which should change theabove-mentioned threshold according to the above-mentioned sendingoperation. When there is a response message to the above-mentionedmessage, an uplink dedicated channel receiving unit 32 receives it.

When the dedicated channel is released in the communications with theterminal 2, the RNC can assign the information about the above-mentionedthreshold to the common channel.

When determining that the dedicated channel is released from themanagement information about the radio resources, the RNC 3 assigns, asa message, the information about the above-mentioned threshold to thecommon channel, and transmits it to the base station.

When receiving the message about the above-mentioned threshold via thecommon channel, the downlink common channel transmitting unit 34disposed in the base station assigns the message to FACH, and transmitsthe message to the terminal 2 which should change the above-mentionedthreshold according to the above-mentioned sending operation. When thereis a response message to the above-mentioned message, an uplink commonchannel receiving unit 33 receives it.

In the above explanation, the scheme for determining a change in theabove-mentioned threshold on the side of the base station is explained.As an alternative, the base station can be so constructed as todetermine the transmission mode itself which should be set to theterminal 2.

In this case, in the above-mentioned signaling operation for changingthe threshold, not the information about the threshold but informationspecifying the transmission mode which should be set to the terminal 2is transmitted to the terminal 2. The details of this processing will bementioned later.

FIG. 11 is a block diagram showing the internal structure of the mobilecommunication terminal shown in FIG. 1, and the fundamental operation ofthe mobile communication terminal will be explained with reference tothis figure. In FIG. 11, in order to prevent redundant description,simplified names are given to formation parts which will be mentionedlater, and the same formation parts as previously mentioned aredesignated by the same reference numerals.

First, processing common to both general CDMA modulation anddemodulation will be explained.

A sending operation will be explained first. A modulating unit 35multiplies signals associated with channels (UL-SICCH, UL-TFRI-CCH,EACH, uplink DPCH, etc.) by a channelization code generated by an uplinkchannelization code generator 36, and then multiplexes these signalsinto a signal. The modulating unit 35 then multiplies the signal intowhich those signals associated the channels are multiplexed by ascrambling code generated by an uplink scrambling code generator 37, andperforms spectrum spread processing on the signal multiplied by thescrambling code.

A baseband signal which is a signal associated with each of the channelsmultiplexed by the modulating unit 5 is outputted to a frequencyconverting unit 38. The frequency converting unit 38 increases thefrequency of the above-mentioned baseband signal to a carrier frequency,and outputs it to a power amplifying unit 39.

The power amplifying unit 39 amplifies the signal furnished thereto fromthe frequency converting unit 38 using an internal power amplifier sothat the signal has desired power. The signal amplified by the poweramplifying unit 39 is transmitted to each of the base stations 4 a and 4b via an antenna 40.

Next, a receiving operation will be explained. A weak signal receivedvia the antenna 40 from a base station is furnished to a low noiseamplifier unit 41. After amplifying this signal, this low noiseamplifier unit 41 outputs the amplified signal to a frequency convertingunit 42. The frequency converting unit 42 reduces the frequency of thesignal furnished thereto from the low noise amplifier unit 41 to thefrequency of the above-mentioned baseband signal.

A back spreading demodulating unit 46 multiplies the baseband signalwhose frequency is frequency-converted by the frequency converting unit42 by a scrambling code generated by the downlink scrambling codegenerator 45 and performs back spreading processing on the result of themultiplication so as to demultiplex the received signal into signalsassociated with channels using a channelization code generated by adownlink channelization code generator 44.

After that, the back spreading demodulating unit 46 outputs a TPCcommand included in the signal received from the base station to a powercontroller 43. The power controller 43 instructs the power amplifyingunit 39 to increase or decrease the transmission power according to theabove-mentioned TPC command, so that the power amplifying unit 39determines the transmission power according to the command.

A signal associated with CPICH among the signals associated withchannels into which the received signal is demultiplexed by the backspreading demodulating unit 46 is received by a common pilot signalreceiving unit 47.

The common pilot signal receiving unit 47 makes the timing fordemodulation coincide with the base station, and supplies a timingsignal indicating the timing to a timing management unit 48. The timingmanagement unit 48 distributes the timing signal supplied from thecommon pilot signal receiving unit 47 to each of the processing unitsdisposed in the mobile communication terminal 2, and performs processingsynchronized with the base station.

Next, a scheme required for the uplink packet communications will beexplained.

First, the operation in the autonomous mode will be explained.

In the operation in the autonomous mode, a transmission permissioninformation receiving unit 49 disposed in the mobile communicationterminal 2 receives the transmission permissible margin from each basestation using DL-SACCH or a similar downlink signaling channel. Thistransmission permissible margin is notified to an uplink packettransmission management unit 51 by the transmission permissioninformation receiving unit 49. In the autonomous mode, the transmissiontiming is arbitrary.

After that, when the user sets data to be transmitted from the mobilecommunication terminal 2 to each base station, the mobile communicationterminal 2 stores the transmission data in a transmission data buffer 58for uplink packet communications.

In the autonomous mode, in order to start transmission immediately, theuplink packet transmission management unit (i.e., a communicationmanagement unit) 51 specifies a TFRI which is suited to the amount ofthe transmission data in consideration of the above-mentionedtransmission permissible margin, and notifies the TFRI to a TFRItransmission processing unit 53.

The TFRI transmission processing unit 53 transmits the TFRI to each basestation according to the above-mentioned sending operation afterassigning the TFRI to UL-TFRI-CCH. As a result, the sending operation iscontrolled so that the noise rise is reduced to within the range ofabove-mentioned transmission permissible margin specified by each basestation.

After converting the data stored in the transmission data buffer 58 foruplink packet communications into data having a transmission formatspecified by the above-mentioned TFRI, a EUDTCH transmission processingunit 52 assigns the data body to EUDTCH and transmits the data body toeach base station according to the above-mentioned sending operation.

When receiving the above-mentioned packet data from the mobilecommunication terminal 2, each base station assigns a response signalindicating a response to this packet data to DL-ACK/NACK-CCH, andtransmits it to the terminal 2. Then, a response signal receiving unit57 of the mobile communication terminal 2 determines whether theresponse signal received via the above-mentioned DL-ACK/NACK-CCHindicates ACK or NACK according to the above-mentioned receivingoperation.

When determining that the response signal indicates ACK, the responsesignal receiving unit 57 notifies the result of the determination to theuplink transmission packet management unit 51. After that, the uplinktransmission packet management unit 51 shifts to a process oftransmitting the next packet data to each base station.

On the other hand, when the response signal receiving unit 57 determinesthat the response signal indicates NACK, the uplink transmission packetmanagement unit 51 shifts to a process of resending the packet data forwhich the response is determined as NACK to each base station. Whenresending the packet data, the EUDTCH transmission processing unit 52causes the packet data have redundancy, such as incremental redundancy,as occasion demands.

Next, the operation in the scheduling mode will be explained.

In the operation in the scheduling mode, when the user sets data whichis to be transmitted from the mobile communication terminal 2 to eachbase station, this transmission data is stored in the transmission databuffer 58 for uplink packet communications.

After that, a buffer state transmission unit 55 which has received acommand from the uplink packet transmission management unit 51 assignsthe amount of the data to be transmitted to each base station, a marginfor the transmission power of the terminal 2, etc. to UL-SICCH, andtransmits them to each base station according to the above-mentionedsending operation.

When receiving the signal associated with UL-SICCH, each base stationdetermines a proper transmission timing at which signals from terminals2 accommodated in the own cell interfere with one another the least inconsideration of the state of the transmission data buffer 58 of each ofthe terminals 2. As a result, each base station assigns a command forgiving permission to transmit packet data at the transmission timing toeach terminal 2 to DL-SACCH and transmits it to each terminal 2,according to the above-mentioned sending operation.

The transmission permission information receiving unit 49 of the mobilecommunication terminal 2 receives information assigned to DL-SACCH,including the transmitting rate, subframe timing, etc., which arepermitted by each base station. This information is then delivered fromthe transmission permission information receiving unit 49 to the timingmanagement unit 48 and uplink packet transmission management unit 51.

The uplink packet transmission management unit 51 specifies TFRI whichis suited to the amount of transmission data, and notifies the TFRI tothe TFRI transmission processing unit 53. The TFRI transmissionprocessing unit 53 assigns the TFRI to UL-TFRI-CCH, and transmits it toeach base station according to the above-mentioned sending operation.

The EUDTCH transmission processing unit 52 reads the data stored In thetransmission data buffer 58 for uplink packet communications, and, afterconverting the data into data having a transmit format specified by theabove-mentioned TFRI which the TFRI transmission processing unit 53 hastransmitted to each base station, assigns the data body to EUDTCH andtransmits it to each base station according to the above-mentionedsending operation.

When receiving the above-mentioned packet data from the mobilecommunication terminal 2, each base station assigns a response signalindicating a response to this packet data to DL-ACK/NACK-CCH andtransmits it to the terminal. The response signal receiving unit 57 ofthe mobile communication terminal 2 determines whether the responsesignal received via the above-mentioned DL-ACK/NACK-CCH indicates ACK orNACK according to the above-mentioned receiving operation.

When determining that the response signal indicates ACK, the responsesignal receiving unit 57 notifies the result of the determination to theuplink transmission packet management unit 51. After that, the uplinktransmission packet management unit 51 shifts to a process oftransmitting the next packet data to each base station.

On the other hand, when the response signal receiving unit determinesthat the response signal indicates NACK, the uplink transmission packetmanagement unit 51 shifts to a process of resending the packet data forwhich the response is determined as NACK to each base station.

When resending the packet data, the EUDTCH transmission processing unit52 causes the packet data to have redundancy, such as incrementalredundancy, as occasion demands.

Then, a scheme required to switch between the transmission modes will beexplained.

First, the uplink packet transmission management unit 51 compares thethreshold provided from a threshold changing unit 50 with the amount ofdata which remain in the transmission data buffer 58 for uplink packetcommunications.

At this time, when the amount of data which remain in the transmissiondata buffer is larger than the threshold, the uplink packet transmissionmanagement unit 51 notifies a transmission mode switching unit 54 thatthe switching between the transmitting modes is completed.

When the switching between the transmission modes by the transmissionmode switching unit 54 is completed, the buffer state transmission unit55 assigns information indicating that the switching between thetransmission modes is completed to UL-SICCH, and transmits it to eachbase station according to the above-mentioned sending operation.

The TFRI transmission processing unit 53 can alternatively assign theinformation indicating that the switching between the transmission modesis completed to UL-TFRU-CCH, and can transmit it to each base station.Furthermore, a protocol processing unit 56 which has received theinformation indicating that the switching between the transmission modesis completed from the transmission mode switching unit 54 notifies theinformation to an uplink dedicated channel transmission unit 60.

As a result, the uplink dedicated channel transmission unit 60 canassign, as a message, the information indicating that the switchingbetween the transmission modes is completed to the uplink DPCH, and cantransmit it to each base station. Thus, the mobile communicationterminal 2 notifies each base station that the switching between thetransmission modes is completed using a certain channel.

Next, a scheme required to change the threshold associated withswitching between the transmission modes will be explained.

First, when notifying a change in the threshold to all terminals 2 inthe own cell all at once, each base station inserts information aboutthe threshold into the broadcast information (BCH) to be transmitted toeach mobile communication terminal 2.

A broadcast information receiving unit 61 of each mobile communicationterminal 2 receives the set of broadcast information from each basestation according to the above-mentioned receiving operation, andnotifies it to the protocol processing unit 56. The protocol processingunit 56 interprets the broadcast information.

At this time, when interpreting the above-mentioned broadcastinformation as a command for changing the above-mentioned threshold ofthe transmission data buffer 58 for uplink packet communications, theprotocol processing unit 56 sets the threshold which is changedaccording to the command to the threshold changing unit 50.

After that, the threshold changing unit 50 notifies the uplink packettransmission management unit 51 of the changed threshold. As a result,in this mobile communication terminal 2, the transmission mode ischanged on the basis of the changed threshold.

Next, a case where the above-mentioned threshold is changed according toa layer-3 message will be explained.

In this case, two channels: the dedicated channel and the common channelcan be considered as channels to be used.

First, changing the threshold using the dedicated channel will beexplained.

The dedicated channel is used to specify the threshold for eachindividual terminal, for example.

The dedicated channel (e.g., a downlink DPCH) to which a message aboutthe above-mentioned threshold delivered from the downlink dedicatedchannel transmission unit 29 of each base station is assigned isreceived by a downlink dedicated channel receiving unit 63 of eachterminal 2, and is notified to the protocol processing unit 56. Theprotocol processing unit 56 interprets the contents associated with thededicated channel.

At this time, when interpreting the message assigned to theabove-mentioned dedicated channel as a command for changing theabove-mentioned threshold, the protocol processing unit 56 sets thethreshold to be changed according to the message to the thresholdchanging unit 50. The threshold changing unit 50 then notifies theuplink packet transmission management unit 51 of the changed threshold.

The uplink dedicated channel transmitting unit 60 assigns, as a message,the information indicating that the transmission mode has been changedto the uplink DPCH, and transmits it to each base station.

A case where the above-mentioned threshold is changed using the commonchannel 30 will be explained.

The common channel is used when the dedicated channel is released andthe above-mentioned threshold is specified for each individual terminal2, for example. Especially, the dedicated channel may be releasedtemporarily to address low power consumption etc. In such a case, thecommon channel is used.

A message assigned to the common channel (FACH) from each base stationis received by a downlink common channel receiving unit 62 according tothe above-mentioned receiving operation. Then, the message is sent fromthe downlink common channel receiving unit 62 to the protocol processingunit 56. The protocol processing unit 56 interprets the above-mentionedmessage.

At this time, when interpreting the message assigned to theabove-mentioned common channel as a command for changing theabove-mentioned threshold, the protocol processing unit 56 sets thethreshold to be changed according to the message to the thresholdchanging unit 50. The threshold changing unit 50 then notifies theuplink packet transmission management unit 51 of the changed threshold.

Furthermore, an uplink common channel transmitting unit 59 assigns, as amessage, information indicating that the transmission mode has beenchanged to RACH, and transmits it to each base station.

Next, a case where the above-mentioned threshold is changed using aphysical-layer signaling will be explained. The physical-layer signalingis to assign information about the above-mentioned threshold to acertain bit of information about a physical layer, which is used forsetting the conditions of communications via the physical layer betweenthe mobile communication terminal 2 and each base station. Thisinformation about the physical layer is assigned to, for example, toDL-SACCH.

The physical-layer signaling is used when specifying the above-mentionedthreshold for each individual terminal 2, for example, and makes itpossible to specify the threshold for each individual terminal at ahigher speed than in the above-mentioned cases.

The transmission permission information receiving unit 49 receives theinformation about the physical layer embedded into DL-SACCH from eachbase station, and notifies it to the protocol processing unit 56. Theprotocol processing unit 56 then interprets the information received bythe transmission permission information receiving unit 49.

At this time, when interpreting the above-mentioned information as acommand for changing the above-mentioned threshold, the protocolprocessing unit 56 sets the threshold to be changed according to theabove-mentioned information to the threshold changing unit 50. Thethreshold changing unit 50 then notifies the uplink packet transmissionmanagement unit 51 of the changed threshold.

FIG. 12 is a block diagram showing the internal structure of the RNCshown in FIG. 1, and the fundamental operation of the RNC 3 will beexplained with reference to this figure. In FIG. 12, in order to preventredundant description, simplified names are given to formation partswhich will be mentioned later, and the same formation parts aspreviously mentioned are designated by the same reference numerals.

A QoS parameter mapping unit 64 selects radio resources for satisfyingQoS (Quality of Service) (e.g., permission for delay times, etc.)specified for communications between the mobile communication terminal 2and each of the base stations 4 a and 4 b, and parameters related to theradio resources. These parameters related to the communications includea mode in an RLC (Radio Link Control) layer, the number of transportblock sizes in the physical layer, the number of CRC (Cyclic RedundancyCheck) bits, etc.

A congestion control unit 65 prevents congestions from occurring IIIcommunications between the mobile communication terminal 2 and each ofthe base stations, and imposes limitations on calls, for example. Aradio resources management unit 66 manages information about radioresources (e.g., channels, power, codes, etc.), and measurement data,and notifies the management information to each base station if neededat the time of communications between the mobile communication terminal2 and each of the base stations. The above-mentioned jamming margin iscomputed by this radio resources management unit 66.

The radio resources management unit (i.e., a communication resourcemanagement unit) 66 also sets the permissible margin in which a marginis incorporated into the above-mentioned jamming margin in considerationof the QoS parameters, such as a delay time, to each base station. Eachbase station executes a command for switching the communication modesfor each terminal 2 accommodated in the own cell thereof, etc. so thatthe noise rise falls within the above-mentioned permissible margin.

In a related art mobile communication system, the conditions ofcommunications between a base station and a terminal, under which thenoise rise falls within the jamming margin, are determined by an RNC,and communications between the base station and the terminal arecontrolled according to the communication conditions notified from theRNC.

An inevitable problem with this related art structure is, however, thatthe quality of the communications between the base station and theterminal is restricted by a communication delay time which occursbetween the RNC and the base station.

On the contrary, in the mobile communication system according to thepresent invention, the RNC sets the permissible margin in which a marginassociated with interference which should be taken into considerationbased on requirements defined by the QoS parameters, such as theoperating states of other cells other than the target cell, and delaytimes, is incorporated into the jamming margin to each base station.

In other words, the range of amounts of interference of theabove-mentioned permissible margin is narrower than the jamming marginby the amount of interference which should be taken into considerationbased on requirements defined by the QoS parameters, such as theoperating states of other cells other than the target cell, and delaytimes.

Then, each base station partially performs a process of determining thecommunication conditions under which the noise rise falls within theabove-mentioned permissible margin. For example, each base stationproperly performs a division of the above-mentioned permissible marginamong margins for the noise rise in all modes according to thecommunication conditions at the current time, and so on.

As a result, each base station can determine the communicationconditions promptly according to the QoS of the communications withterminals completely-independently upon the communication conditionsnotified from the RNC, and makes it possible to carry out efficient datacommunications according to a change in the noise rise which is causedby a change in the communication load.

A core network protocol processing unit 67 processes protocols used incommunications with the network. A radio network protocol processingunit 68 processes protocols used in communications with each of the basestations.

Next, the operation of the mobile communication system according toembodiment 1 will be explained.

As previously explained, when transmission data having an amountexceeding the threshold used for switching between the communicationmodes remains in the transmission data buffer of the mobilecommunication terminal 2, the mobile communication terminal 2 switchesto the scheduling mode, whereas the amount of transmission data whichremains in the transmission data buffer of the mobile communicationterminal 2 becomes smaller than the threshold, the mobile communicationterminal 2 switches to the autonomous mode. Hereinafter, three methodsof performing a signaling for changing the threshold will be explained.

The first method is the one of setting change information about a changein the above-mentioned threshold to broadcast information, and notifyingit to all terminals 2 staying in the cell all at once to change thethreshold of each of the terminals. The second method is the one ofassigning change information about a change in the above-mentionedthreshold to the dedicated channel or common channel, and notifying itto each individual terminal 2 to change the threshold of the terminal.The third method is the one of notifying change information about achange in the above-mentioned threshold to each terminal 2 byphysical-layer signaling to change the threshold of each terminal.

First, the first method will be explained.

According to this method, adjustment of a proper division of the noiserise in the own cell can be carried out by changing the thresholdaccording to the number of terminals placed in the scheduling mode andcurrently staying in the own cell, the number of terminals placed in theautonomous mode and currently staying in the own cell, and the operationconditions of those terminals, and the operation conditions of thededicated channel.

FIG. 13 is a diagram showing an example of a division of the noise risemargin of each base station when the RNC according to embodiment 1determines the threshold for switching between the transmission modes ofeach terminal according to the first method, and FIG. 14 is a diagramexplaining a change in the threshold for switching between thetransmission modes which is based on the division of the noise risemargin shown in FIG. 13. The basic concept underlying the first methodwill be explained with reference to these figures. First, assume that aplurality of mobile communication terminals 2 are accommodated in thecell of a base station before the threshold for switching between thetransmission modes of each of the plurality of terminals is changed.Furthermore, assume that the noise rise margin of the base station isdivided into the permissible margin for the noise rise resulting fromthe autonomous mode, the permissible margin for the noise rise resultingfrom the scheduling mode, and the permissible margin (another area shownin the figure and associated with the dedicated channel, and so on) forthe noise rise resulting from transmission via the dedicated channel,and so on, as shown in FIG. 13( a).

In this case, the above-mentioned noise rise margin of the base stationis the permissible margin in which a margin associated with interferencewhich should be taken into consideration based on the operating statesof other cells and QoS is incorporated into the above-mentioned jammingmargin.

At this time, assume that the above-mentioned threshold of thetransmission data buffer of each mobile communication terminal 2 has arelationship, as shown in FIG. 14( a), with the transmission data storedin the buffer.

Assume that a certain amount of data transmission is carried out via thededicated channel. At this time, the RNC 3 performs managementprocessing to secure a required permissible margin for the noise riseresulting from the data transmission via the dedicated channel.

Therefore, when the frequency of occurrence of data transmission via thededicated channel between a terminal 2 and the base station increases,the RNC 3 instructs the base station to increase the permissible marginrequired to carry out transmission of data to the terminal via thededicated channel.

Data transmission via the dedicated channel is carried out for eachterminal 2. For this reason, when the frequency of occurrence of datatransmission via the dedicated channel increases, the permissible marginassociated with the dedicated channel is secured from the permissiblemargin assigned to each terminal 2 which is included in the noise risemargin of the base station.

As a result, as shown in FIG. 13( b), the permissible margin assigned tothe noise rise resulting from the autonomous mode, which is included inthe noise rise margin of the base station, is reduced by the increase inthe permissible margin associated with the dedicated channel. At thistime, when the number of terminals in the cell does not vary, the noiserise margin per terminal decreases.

In this case, when a relatively small threshold for switching betweenthe transmission modes is set to the transmission data buffer of eachterminal, as shown in FIG. 14( a), there is a possibility thattransmission of data having an amount exceeding the permissible marginin the autonomy is performed.

In other words, in the case where the threshold as shown in FIG. 14( a)is maintained, a terminal 2 which is going to transmit a large amount ofdata to each base station will be unable to accept the noise rise causedby the data transmission.

Then, when the noise rise margin is divided as shown in FIG. 13( b), byreducing the thresholds of the transmission data buffers of allterminals 2 accommodated in the cell all at once using the broadcastinformation according to the first method, as shown in FIG. 14( b), anyterminal 2 which is going to transmit data having a large amount is madeto switch from the autonomous mode to the scheduling mode.

At this time, any terminal 2 which is going to perform transmission ofdata having a small amount is held in the autonomous mode if the amountof transmission data does not exceed the changed threshold value.

Since the balance between the number of terminals placed in theautonomous mode and the number of terminals placed in the scheduling maybe lost if the threshold is lowered too much at a time, it is desirableto reduce the threshold step by step.

FIG. 15 is a diagram showing a changing sequence for changing thethreshold of a transmission data buffer according to the first method inthe mobile communication system according embodiment 1. Each basestation measures the noise rise at an end thereof at the current time(in step ST1). To be more specific, as shown in FIG. 10, the noise rise(the amount of interference) at each base station's end at the currenttime is measured by the desired wave power measurement unit 16 andinterference wave power measurement unit 17 of each base station.

After that, each base station notifies the noise rise measured in stepST1 to the RNC 3 (in step ST2). Each base station further notifies boththe number of terminals in the own cell which are operating in theautonomous mode and the number of terminals in the own cell which areoperating in the scheduling mode to the RNC 3 (in step ST3).

Then, the radio resources management unit 66 of the RNC 3 acquiresinformation about the operation conditions of other base stations whichexist around the target base station (referred to as neighboring basestations from here on) (the operation conditions including, for example,the number of terminals accommodated in the cell of each of theneighboring base stations) (in step ST4).

When a large number of terminals 2 are operating in the neighboring basestations, there is a possibility that a terminal 2 moves to an areawhere a handover is performed. In this case, the radio resourcesmanagement unit 66 of the RNC 3 further incorporates a margin which isdetermined in consideration of a noise rise resulting from the handoverto the jamming margin, as the permissible margin which is notified tothe base station in question.

Then, the radio resources management unit 66 acquires information aboutthe operation conditions of the dedicated channel in the base station inquestion (in step ST5). Usually, since the dedicated channel is used inorder to carry out transmission of data from a neighboring base stationto the terminal 2 in the soft handover, the RNC 3 grasps the operationconditions of the dedicated channel.

The radio resources management unit 66 determines whether the noise risemargin of the base station in question is enough or short compared withthe noise rise at the current time which is acquired in steps ST1 to ST5(in step ST6). According to the result of the determination, the radioresources management unit 66 shifts to a process of changing both anoise rise limit for the autonomous mode and a noise rise limit for thescheduling mode.

Here, a noise rise limit is referred to as a part of the noise risemargin which is assigned to each mode, the noise rise margin beingspecified and divided, as the above-mentioned permissible margin, forthe base station by the RNC 3. In FIG. 13, for example, an area which isshaded as the margin in the scheduling mode shows the noise rise limitfor the scheduling mode.

When determining that the noise rise margin of the base station is toolarge or too small with respect to the noise rise at the current timeand the noise rise limits currently being assigned in the base stationhave to be changed, the radio resources management unit 66 instructs thebase station to change the noise rise limit for the autonomous modeand/or for the scheduling mode (in step ST7).

On the other hand, when determining that the noise rise margin of thebase station is neither too large nor too small with respect to thenoise rise at the current time and the noise rise limits currently beingassigned in the base station don't have to be changed, the radioresources management unit 66 does not provide any changing command forchanging the above-mentioned noise rise limits.

When receiving the changing command for changing the noise rise limitsfrom the RNC 3, the base station changes the noise rise limits accordingto the changing command (in step ST8). For example, when the frequencyof data transmission using the dedicated channel increases, as explainedwith reference to FIG. 13, the RNC 3 instructs the base station toincrease the noise rise limit associated with the dedicated channelwhich is included in the noise rise margin of the base station, andhence to reduce the noise rise limit for the autonomous mode by theincrease in the noise rise limit associated with the dedicated channel.

Then, when receiving a notification that the threshold for switchingbetween the transmission modes of each terminal 2 should be changed fromthe base station, the radio resources management unit 66 determines whatvalue the above-mentioned threshold should be changed to so that thereoccurs a proper amount of interference in the communications between thebase station and each terminal 2 by taking into consideration thetraffic conditions at the current time, the noise rise in the basestation in question and the permissible margin for the noise rise (instep ST9).

After that, the radio resources management unit 66 notifies informationabout the change in the above-mentioned threshold, the informationincluding the threshold value which is determined, to theabove-mentioned base station (in step ST10).

When receiving the information about the change in the above-mentionedthreshold from the RNC 3, the base station sets the informationcontaining the above-mentioned threshold value to broadcast information(BCH), and broadcasts it to each terminal 2 (in step ST11).

When receiving the broadcast information, each terminal 2 reads thethreshold value for switching between the transmission modes from thebroadcast information and changes the above-mentioned threshold, as inthe case of the operation explained with reference to FIG. 11 (in stepST12).

The process of step ST9 shown in FIG. 15 of the mobile communicationsystem according to embodiment 1 will be explained in detail withreference to a flow chart shown in FIG. 16.

First, the uplink packet transmission management unit 24 of the basestation compares the amount of data of a transmission data buffer, whichis notified from a terminal 2 staying in the own cell, and theabove-mentioned threshold value set to the above-mentioned terminal 2 soas to determine whether to change the above-mentioned threshold value.When determining that the above-mentioned threshold value should bechanged, the base station notifies the RNC 3 that the threshold valueshould be changed according to the above-mentioned sending operation.

In step ST1 a, the radio resources management unit 66 of the RNC 3 whichhas received the notification that the threshold should be changed fromthe base station estimates the noise rise resulting from the datatransmission via the dedicated channel based on the operation conditionsof the dedicated channel in the base station in question.

Next, the radio resources management unit 66 estimates the permissiblemargin for the noise rise according to the current operating states ofother base stations other than the above-mentioned base station (in stepST2 a). For example, when there exist many terminals in the neighboringbase stations, there is a possibility that a terminal 2 moves to an areawhere a handover is performed. In this case, the radio resourcesmanagement unit 66 estimates the margin in consideration of a noise riseresulting from the handover.

When thus determining the margin in consideration of the operatingstates of the neighboring base stations (e.g., determining the margin inconsideration of that there exist many terminals in the neighboring basestations, etc.), the radio resources management unit 66 incorporates thedetermined margin into the permissible margin for the noise rise, whichis set to the base station.

That is, the radio resources management unit defines a margin which isobtained by subtracting the margin which is determined in considerationof the operating states of the neighboring base stations, etc. from theabove-mentioned permissible margin as a new permissible margin whichshould be set to the base station.

Then, the radio resources management unit 66 acquires the noise rise inthe scheduling mode in the cell of the above-mentioned base station andthe number of terminals staying in the cell (in step ST3 a). After that,the radio resources management unit 66 estimates the permissible marginfor each of the noise rise resulting from the data transmission via thededicated channel which is acquired in step ST1 a, and the noise rise inthe scheduling mode in the cell of the above-mentioned base stationwhich is acquired in step ST3 a.

In step ST4 a, the radio resources management unit 66 subtracts both themargin associated with the dedicated channel, and the margin in thescheduling mode from the whole permissible margin of the above-mentionedbase station in which the margin which is determined in consideration ofthe operating states of the neighboring base stations is allowed for instep ST2 a, and then determines the permissible margin (i.e., the noiserise limit) for the noise rise in the autonomous mode in theabove-mentioned base station.

Next, the radio resources management unit 66 determines whether or notthe number of terminals which are operating in the autonomous mode inthe cell of the above-mentioned base station is appropriate with respectto the noise rise limit for the autonomous mode in the above-mentionedbase station, which is acquired in step ST4 a (in step ST5 a).

The base station is notified of the amount of transmission data of thetransmission data buffer of each terminal 2 in the own cell from eachterminal 2. The RNC 3 is notified of the above-mentioned amount oftransmission data from the base station. The radio resources managementunit 66 of the RNC 3 computes the average of the amounts of transmissiondata of all terminals 2 staying in the cell of the base station inadvance by summing plural data amounts notified thereto from the basestation for a predetermined period.

Furthermore, the radio resources management unit 66 statisticallydetermines how much noise rise limit for the autonomous mode in the basestation with respect to the above-mentioned average of the amounts oftransmission data of all the terminals 2 causes what percentage of thetotal number of terminals to carry out transmission of data which cannotbe demodulated to the base station beyond the noise rise limit.

For example, a case where the ratio of the number of terminals whichcarry out transmission of data which cannot be demodulated to the basestation beyond the noise rise limit for the autonomous mode to the totalnumber of terminals exceeds a specific percentage is defined as a statein which the number of terminals in the autonomous mode is too large, acase where the ratio is equal to or less than the specific percentage isdefined as a state in which the number of terminals in the autonomousmode is too small, and any other cases are defined as a state in whichthe number of terminals in the autonomous mode is appropriate.

In step ST5 a, the radio resources management unit 66 checks to see howmuch noise rise limit for the autonomous mode in the base station at thecurrent time is provided with respect to the above-mentioned average,and then determines whether or not the number of terminals placed in theautonomous mode is appropriate based on the result of the checking.

When, in step ST5 a, determining that the number of terminals placed inthe autonomous mode is too large, the radio resources management unit 66reduces the threshold value for switching the transmission modes whichis set to each terminal 2 at the current time (in step ST6 a). The noiserise margin which is assigned to the plurality of terminals 2 placed inthe autonomous mode is divided among the plurality of terminals placedin the autonomous mode according to the number of the terminals so as tofall within the noise rise limit for the autonomous mode in the basestation.

Therefore, since the noise rise limit for the autonomous mode in thebase station is fixed, the noise rise margin which is assigned to eachof the terminals 2 placed in the autonomous mode decreases as the numberof the terminals placed in the autonomous mode increases.

For this reason, when the noise rise margin which is assigned to eachterminal 2 decreases, a terminal 2 may perform data transmission at adata rate which is suited to the amount of transmission data thereofwith the noise rise caused by the data transmission exceeding thepermissible margin having a range in which data can be demodulated.Thus, such the state in which the number of terminals staying in thecell and placed in the autonomous mode exceeds the number of terminalsto each of which the permissible margin having a range in which data canbe demodulated is provided is defined as the state in which the numberof terminals staying in the cell and placed in the autonomous mode islarge.

When, in step ST6 a, reducing the threshold value, the radio resourcesmanagement unit 66 shifts to the process of step ST10 of FIG. 15 inwhich it notifies the changed threshold value, as the information aboutthe change in the threshold, to the above-mentioned base station.

When, in step ST5 a, determining with the number of the terminals placedin the autonomous mode is appropriate, the radio resources managementunit 66 maintains the current threshold value for switching between thetransmission modes (in step ST7 a). This threshold value is notified, asthe information about the change in the threshold, to the base stationin step ST10 of FIG. 15.

When, in step ST5 a, determining that the number of the terminals placedin the autonomous mode is too small, the radio resources management unit66 raises the threshold value for switching between the transmissionmodes which is currently set to each terminal 2 (in step ST8 a). Thestate in which the number of terminals placed in the autonomous mode istoo small is the one in which a margin more than needed can be providedfor the noise rise margin assigned to each terminal 2 even if eachterminal 2 performs data transmission at a data rate which is suited tothe amount of transmission data thereof.

In this case, if the number of terminals staying in the cell and placedin the autonomous mode is made to increase by increasing the thresholdvalue, the noise rise margin assigned to each terminal 2 can be usedeffectively.

Thus, when, in step ST8 a, increasing the threshold value, the radioresources management unit 66 shifts to the process of step ST10 of FIG.15 in which it notifies the changed threshold value, as the informationabout the change in the threshold, to the above-mentioned base station.

When the change in the threshold value which is decreased or increasedat a time in step ST6 a or ST8 a is too large, a larger number ofterminals 2 than needed can be made to switch between the transmissionmodes.

Then, it is desirable to make the change in the threshold value which islowered or raised at a time fall within a range of constant values inconsideration of the number of the terminals staying in the cell andplaced in the autonomous mode etc., and to change the above-mentionedthreshold value step by step.

As mentioned above, according to the first method, the change in thethreshold value for switching between the transmission modes can benotified to all terminals staying in the cell all at once. For thisreason, the number of times that the signaling for notifying theabove-mentioned change in the threshold value is carried out can bereduced.

The signaling using the above-mentioned broadcast information has adisadvantage that it is impossible to set a different threshold value toeach terminal 2. To solve this problem, all terminals 2 staying in thecell can be divided into a plurality of groups based on, for example,QoS classes, and the above-mentioned threshold can be set to each group.

A concrete method of dividing all terminals staying in the cell into aplurality of groups will be explained.

In the W-CDMA system, four QoS classes (e.g., a conversational-modeclass, a streaming class, an interactive class, and a background class)are defined. For example, assume that all terminals 2 staying in thecell are divided into three groups as explained below based oncommunication delay tolerances associated with these QoS classes.

The first group is the group to which a conversational-mode class and astreaming class belong, the group using a communication service whichhandles data, such as audio data and moving image data, which refuse anydelay most strongly.

The second group is the group to which an interactive class belongs, thegroup using a communication service which permits a delay time to someextent. For example, a still image, a text file, etc. which are offeredby WWW (World Wide Web) etc. are handled by the second group. When suchdata is transmitted to a terminal of the second group, a communicationdelay time is permitted to some extent, but it is not necessarilyaccepted fully, and a too large delay time may give the userdispleasure.

The third group is the group to which a background class belongs, thegroup using a communication service which permits a delay time. Forexample, a terminal which is carrying out a data transfer using FTP(File Transfer Protocol) which requires scheduling about communicationsand permits a delay time belongs to the third group.

The division of all terminals 2 staying in the cell into the groups isperformed by the QoS parameter mapping unit 64 of the RNC 3 which graspsthe QoS classes in communications with the base station. The result ofthe division is also held by the QoS parameter mapping unit 64.

Next, the process of changing the threshold for terminals 2 which areclassified into one of the groups as mentioned above will be explained.

When receiving a notification indicating that the threshold for aspecific terminal should be changed from a base station, the radioresources management unit 66 of the RNC 3 determines to which group theterminal 2 for which the above-mentioned threshold should be changedbelongs based on the result of the division currently being held by theQoS parameter mapping unit 64.

The radio resources management unit 66 determines an increase ordecrease in the threshold value which is to be set to each group basedon the result of the division. For example, the radio resourcesmanagement unit controls the threshold for a terminal 2 belonging to thefirst group which refuses any delay time most strongly so that thethreshold is maximized. The radio resources management unit alsocontrols the threshold for a terminal 2 belonging to the third groupwhich permits a delay time so that the threshold is minimized.

When the radio resources management unit determines an increase ordecrease in the threshold value which is to be set to terminals of eachgroup in this way, for example, a terminal belonging to the first groupwhich refuses any delay time most strongly is made to switch to theautonomous mode in which a delay time occurs most scarcely.

When the number of terminals placed in the autonomous mode increases andthe noise rise limit for the scheduling mode is running short in thefirst group, the radio resources management unit can control terminalsin the first group having a large amount of transmission data so as tomake them switch to the scheduling mode by decreasing the thresholdvalue step by step.

The radio resources management unit can also set a smaller threshold tothe second and third groups which permit a delay time, as compared withthe threshold set to the first group so that terminals included in thesecond and third groups switch to the scheduling mode.

However, when the number of terminals belonging to the first groupwithin the cell is small and the permissible margin of the base stationis enough, the radio resources management unit can also raise thethreshold which is to be set to the second and third groups in order touse the permissible margin more effectively.

In addition, when most of all the terminals 2 staying in the cell belongto the first group, all the terminals can be divided into subdividedgroups based on an amount of delay showing how much delay time can beaccepted by data which are handled by each terminal 2.

Next, the second method will be explained.

According to this method, each individual terminal can be switched to anoptimal transmission mode by setting change information about a changein the threshold for switching between the transmission modes to alayer-3 message via a channel, such as the dedicated channel or commonchannel.

FIG. 17 is a diagram showing an example of a division of the noise risemargin of a base station when the RNC according to embodiment 1determines the threshold for switching between the transmission modes ofeach individual terminal according to the second method, and FIG. 18 isa diagram explaining a change in the threshold for switching between thetransmission modes which is based on the division of the noise risemargin shown in FIG. 17. The basic concept underlying the second methodwill be explained with reference to these figures.

First, assume that a plurality of mobile communication terminals 2 areaccommodated in the cell of a base station before the threshold forswitching between the transmission modes of each individual terminal ischanged. The noise rise margin of the base station is divided into thepermissible margin for the noise rise resulting from the autonomousmode, the permissible margin for the noise rise resulting from thescheduling mode, and the permissible margin (another area shown in thefigure and associated with the dedicated channel, and so on) for thenoise rise resulting from transmission via the dedicated channel, and soon, as shown in FIG. 17( a).

In this case, the above-mentioned noise rise margin of the base stationis the permissible margin in which a margin associated with interferencewhich should be taken into consideration based on the operating statesof other cells and QoS is incorporated into the above-mentioned jammingmargin.

At this time, assume that the above-mentioned threshold of thetransmission data buffer of each mobile communication terminal 2 has arelationship, as shown in FIG. 18( a), with the transmission data storedin the buffer.

Assume that a certain amount of data transmission is carried out via thededicated channel. At this time, the RNC 3 performs managementprocessing to secure a required permissible margin for the noise riseresulting from the data transmission via the dedicated channel.

Therefore, when the frequency of occurrence of data transmission via thededicated channel between a terminal 2 and the base station increases,the RNC 3 instructs the base station to increase the permissible marginrequired to carry out transmission of data to the terminal via thededicated channel.

Data transmission via the dedicated channel is carried out for eachterminal 2. For this reason, when the frequency of occurrence of datatransmission via the dedicated channel increases, the permissible marginassociated with the dedicated channel is secured from the permissiblemargin assigned to each terminal 2 which is included in the noise risemargin of the base station.

As a result, as shown in FIG. 17( b), the permissible margin for thenoise rise resulting from the autonomous mode, which is included in thenoise rise margin of the base station, is reduced by the increase in thepermissible margin associated with the dedicated channel.

In this case, when a threshold as shown in FIG. 18( a) for switchingbetween the transmission modes is kept to be set to the transmissiondata buffer of each terminal, there is a possibility that transmissionof data having an amount exceeding the permissible margin in theautonomy is carried out.

In other words, in the case where the threshold as shown in FIG. 18( a)is kept, a terminal 2 which is going to transmit a large amount of datato the base station will be unable to accept the noise rise caused bythe data transmission.

For this reason, as shown in FIGS. 18( b) and 18(c), it is necessary toreduce the threshold value for switching between the communicationmodes. However, when reducing the threshold value for switching betweenthe communication modes, requirements on the communication quality ofeach terminal 2 should be taken into consideration. For example, whetheror not a delay time is permitted depends on the nature of data which ishandled by each terminal 2.

In a QoS class division of communication services in the W-CDMA method,a real time nature is requested of a conversational-mode class whichhandles data such as audio data, and a streaming class which handlesdata such as moving image data in order to prevent the occurrence of adelay time from making the user have an unnatural feeling. Therefore, inthese QoS classes, it is necessary to reduce the delay time if possible.

On the other hand, in an interactive class which handles data such asWeb data, and a background class which handles data transfer accordingto FTP or the like, although the accuracy of transmission data isrequired, it is rare for a delay time to be recognized by the user. Forthis reason, such a data transmission is handled with the best effort,and even if there occurs a delay time, this delay time counts fornothing.

Then, by changing the threshold for each individual terminal 2 using thesecond method, the decrease in the threshold value of the transmissiondata buffer, as shown in FIG. 18( b), of a terminal 2 which handles datawhich does not permit any delay time is reduced so that theabove-mentioned threshold is prevented from decreasing too much.

In contrast, the decrease in the threshold value of the transmissiondata buffer, as shown in FIG. 18( c), of a terminal 2 which handles datawhich can permit a delay time is increased so that the threshold islowered as compared with the case shown in FIG. 18( b).

When the threshold is lowered in this way, a terminal 2 which handlesdata which does not permit any delay can be held in the autonomous modehaving a communication characteristic of producing a delay time moredifficulty than in the scheduling mode, and only a terminal 2 whichhandles data which can permit a delay time can be guided from theautonomous mode to the scheduling mode.

At this time, as shown in FIG. 17( b), for the permissible margin in theautonomous mode in the base station, the decrease in the permissiblemargin assigned to each terminal 2 which handles data which does notpermit any delay time (i.e., the noise rise margin assigned to eachterminal which does not permit any delay time) is reduced, while thedecrease in the permissible margin assigned to each terminal 2 whichhandles data which can permit a delay time (i.e., the noise rise marginassigned to each terminal which can permit a delay time) is increased.

Since the balance between the number of terminals placed in theautonomous mode and the number of terminals placed in the scheduling maybe lost if the threshold is lowered too much at a time, it is desirableto reduce the threshold step by step.

FIG. 19 is a diagram showing a changing sequence for changing thethreshold of a transmission data buffer according to the second methodin the mobile communication system according embodiment 1. Each basestation measures the noise rise at an end thereof at the current time(in step ST1 b). To be more specific, as shown in FIG. 10, the noiserise (the amount of interference) at each base station's end at thecurrent time is measured by the desired wave power measurement unit 16and interference wave power measurement unit 17 of each base station.

After that, each base station notifies the noise rise measured in stepST1 b to the RNC 3 (in step ST2 b). Each base station further notifiesboth the number of terminals staying in the own cell which are operatingin the autonomous mode and the number of terminals staying in the owncell which are operating in the scheduling mode to the RNC 3 (in stepST3 b).

Then, the radio resources management unit 66 of the RNC 3 acquiresinformation about the operation conditions of neighboring base stations(including, for example, the number of terminals accommodated in thecell of each of the neighboring base stations) (in step ST4 b).

When a large number of terminals 2 are operating in the neighboring basestations, there is a possibility that a terminal 2 moves to an areawhere a handover is performed. In this case, the radio resourcesmanagement unit 66 of the RNC 3 further incorporates a margin which isdetermined in consideration of a noise rise resulting from the handoverto the jamming margin to generate the permissible margin which is to benotified to the base station in question.

Then, the radio resources management unit 66 acquires information aboutthe operation conditions of the dedicated channel in the base station inquestion (in step ST5 b). Usually, since the dedicated channel is usedin order to carry out transmission of data from a neighboring basestation to the terminal 2 in a soft handover, the RNC 3 grasps theoperation conditions of the dedicated channel.

The radio resources management unit 66 determines whether the noise risemargin of the base station in question is enough or short compared withthe noise rise at the current time which is acquired in steps ST1 b toST5 b (in step ST6 b). According to the result of the determination, theradio resources management unit 66 shifts to a process of changing boththe noise rise limit for the autonomous mode and the noise rise limitfor the scheduling mode.

When determining that the noise rise margin of the base station is toolarge or too small with respect to the noise rise at the current timeand the noise rise limits currently being assigned in the base stationhave to be changed, the radio resources management unit 66 instructs thebase station to change the noise rise limit for the autonomous modeand/or for the scheduling mode (in step ST7 b).

On the other hand, when determining that the noise rise margin of thebase station is neither too large nor too small with respect to thenoise rise at the current time and the noise rise limits currently beingassigned in the base station don't have to be changed, the radioresources management unit 66 does not provide any changing command forchanging the above-mentioned noise rise limits.

When receiving the changing command for changing the noise rise limitsfrom the RNC 3, the base station changes the noise rise limits accordingto the changing command (in step ST8 b). For example, when the frequencyof data transmission using the dedicated channel increases, as explainedwith reference to FIG. 17, the RNC 3 instructs the base station toincrease the noise rise limit for the dedicated channel which isincluded in the noise rise margin of the base station, and hence toreduce the noise rise limit for the autonomous mode by the increase inthe noise rise limit for the dedicated channel.

Then, when receiving a notification that the threshold for switchingbetween the transmission modes of a target terminal 2 should be changedfrom the base station, the radio resources management unit 66 determineswhat value the above-mentioned threshold of the target terminal 2 shouldbe changed to by taking into consideration the traffic conditions at thecurrent time, the noise rise in the base station in question and thepermissible margin for the noise rise (in step ST9 b).

After that, the radio resources management unit 66 notifies, as alayer-3 message, information about the change in the above-mentionedthreshold, the information including the threshold value which isdetermined, to the above-mentioned base station (in step ST10 b).

When receiving the information about the change in the above-mentionedthreshold from the RNC 3, the base station transmits the above-mentionedinformation to the target terminal 2 to which the changed threshold isto be set using the dedicated channel (DPCH) when communications withthe terminals 2 via the dedicated channel (DPCH) are established,whereas when no communications with the terminals 2 via the dedicatedchannel are established, the base station transmits the above-mentionedinformation to the target terminals 2 using the common channel (FACH)(in step ST11 b).

When receiving the information, the target terminal 2 reads the changedthreshold value for switching between the transmission modes from theinformation assigned to the dedicated channel or common channel andchanges the above-mentioned threshold thereof in the same way that itperforms the operation explained with reference to FIG. 11 (in step ST12b).

After that, the uplink dedicated channel transmitting unit 60 of thetarget terminal 2 assigns, as a message, information indicating that thetarget terminal has changed the threshold value for switching betweenthe transmission modes to the uplink DPCH or RACH, and transmits it tothe base station (step ST13 b). When receiving the message, the basestation notifies the RNC 3 that the above-mentioned change has beencompleted (in step ST14 b).

The process of step ST9 b shown in FIG. 19 of the mobile communicationsystem according to embodiment 1 will be explained in detail withreference to a flow chart shown in FIG. 20.

First, the uplink packet transmission management unit 24 of the basestation compares the amount of data of a transmission data buffer, whichis notified from the target terminal 2 staying in the own cell, with theabove-mentioned threshold value set to the above-mentioned terminal 2 soas to determine whether to change the above-mentioned threshold value.When determining that the above-mentioned threshold value should bechanged, the base station notifies the RNC 3 that the threshold valueshould be changed according to the above-mentioned sending operation.

In step ST1 c, the radio resources management unit 66 of the RNC 3 whichhas received the notification that the threshold should be changed fromthe base station estimates a noise rise resulting from the datatransmission via the dedicated channel based on the operation conditionsof the dedicated channel in the base station in question.

Next, the radio resources management unit 66 estimates the permissiblemargin for the noise rise according to the current operating states ofother base stations other than the above-mentioned base station (in stepST2 c). For example, when there exist many terminals in the neighboringbase stations, there is a possibility that a terminal 2 moves to an areawhere a handover is performed. In this case, the radio resourcesmanagement unit 66 estimates the margin in consideration of a noise riseresulting from the handover.

When thus determining the margin in consideration of the operatingstates of the neighboring base stations (e.g., determining the margin inconsideration of that there exist many terminals in the neighboring basestations, etc.), the radio resources management unit 66 incorporates thedetermined margin into the permissible margin for the noise rise, whichis set to the base station.

That is, the radio resources management unit defines a margin which isobtained by subtracting the margin which is determined in considerationof the operating states of the neighboring base stations, etc. from theabove-mentioned permissible margin as a new permissible margin whichshould be set to the base station.

Then, the radio resources management unit 66 acquires the noise rise inthe scheduling mode in the cell of the above-mentioned base station andthe number of terminals staying in the cell (in step ST3 c). After that,the radio resources management unit 66 estimates the permissible marginfor each of the noise rise resulting from the data transmission via thededicated channel which is acquired in step ST1 c, and the noise rise inthe scheduling mode in the cell of the above-mentioned base stationwhich is acquired in step ST3 c.

In step ST4 c, the radio resources management unit 66 subtracts both themargin associated with the dedicated channel, and the margin associatedwith the scheduling mode from the whole permissible margin of theabove-mentioned base station in which the margin which is determined inconsideration of the operating states of the neighboring base stationsis allowed for in step ST2 c, and then determines the permissible margin(i.e., the noise rise limit) for the noise rise in the autonomous modein the above-mentioned base station.

At this time, when receiving requirements on the transmission data ratefrom each terminal 2, the radio resources management unit 66 adjusts thepermissible margin (i.e., the permissible limit) associated with thescheduling mode in consideration of the requirements on the transmissiondata rate (in step ST5 c).

When transmitting data to a base station in the scheduling mode, eachterminal 2 notifies the transmission data rate which it desires to thebase station in question. The uplink packet transmission management unit24 of the base station manages a schedule of the data communications, aswell as the transmission data rate which is requested by the terminal 2in question.

The uplink packet transmission management unit 24 notifies thetransmission data rate which is requested by the terminal 2 in questionto the radio resources management unit 66 of the RNC 3.

The radio resources management unit 66 estimates the noise riseaccording to the transmission data rate which is requested by theterminal 2 operating in the scheduling mode within the own cell, anddetermines the permissible margin according to the estimated noise riseso as to adjust the permissible margin associated with the schedulingmode.

After that, the radio resources management unit 66 adjusts thepermissible margin associated with the autonomous mode which isdetermined in step ST4 c using the permissible margin associated withthe scheduling mode which is adjusted as mentioned above.

Next, the radio resources management unit 66 determines whether or notthe number of terminals which are operating in the autonomous modewithin the cell of the above-mentioned base station is appropriate withrespect to the noise rise limit for the autonomous mode in theabove-mentioned base station, which is determined as mentioned above (instep ST6 c).

The base station is notified of the amount of transmission data of thetransmission data buffer of each terminal 2 staying in the own cell fromeach terminal 2. The RNC 3 is notified of the above-mentioned amount oftransmission data from the base station. The radio resources managementunit 66 of the RNC 3 computes the average of the amounts of transmissiondata of all terminals 2 staying in the cell of the base station inadvance by summing plural data amounts notified thereto from the basestation for a predetermined period.

Furthermore, the radio resources management unit 66 statisticallydetermines how much noise rise limit for the autonomous mode in the basestation with respect to the above-mentioned average of the amounts oftransmission data of all the terminals 2 causes what percentage of thetotal number of terminals to carry out transmission of data which cannotbe demodulated to the base station in question beyond theabove-mentioned noise rise limit.

For example, a case where the ratio of the number of terminals whichcarry out transmission of data which cannot be demodulated to the basestation beyond the noise rise limit for the autonomous mode to the totalnumber of terminals exceeds a specific percentage is defined as a statein which the number of terminals in the autonomous mode is too large, acase where the ratio is equal to or less than the specific percentage isdefined as a state in which the number of terminals in the autonomousmode is too small, and any other cases are defined as a state in whichthe number of terminals in the autonomous mode is appropriate.

In step ST6 c, the radio resources management unit 66 checks to see howmuch noise rise limit for the autonomous mode in the base station at thecurrent time is provided with respect to the above-mentioned average,and then determines whether or not the number of terminals placed in theautonomous mode is appropriate based on the result of the checking.

When the radio resources management unit 66 determines that there aretoo many terminals placed in the autonomous mode, the QoS parametermapping unit 64 of the RNC 3 searches for a terminal 2 which is placedin the autonomous mode and permits a delay time (in step ST7 c).

As mentioned above, the state in which the number of terminals stayingin the cell and placed in the autonomous mode exceeds the number ofterminals to each of which the permissible margin having a range inwhich data can be demodulated is provided is defined as the state inwhich the number of terminals staying in the cell and placed in theautonomous mode is large.

The QoS parameter mapping unit 64 determines whether or not each ofthese terminals 2 which is operating in the autonomous mode is handlingdata which permits a delay time based on the QoS class to which each ofthe terminals 2 belongs. For example, the QoS parameter mapping unitdetermines whether or not a delay time is permitted based on theabove-mentioned four QoS classes. In the W-CDMA system, since the amountof delay (i.e., a transfer delay) is defined in units of ms, the QoSparameter mapping unit can determine how much delay time can bepermitted based on the amount of delay.

Then, the radio resources management unit 66 sets either the currentthreshold value for switching or a threshold value, which is lowered bya smaller value than that determined in the case of setting a thresholdto a terminal which permits a delay time, to each terminal 2 which hasbeen determined as being a terminal which does not permit any delay timeby the QoS parameter mapping unit 64 in step ST7 c (in step ST10 c).

The radio resources management unit 66 enlarges the amount of reductionin the threshold value for switching which is to be set to a terminalhaving a larger amount of delay (i.e., a looser limitation imposed ondelay time), as a QoS parameter, among terminals 2 belonging to a QoSclass which does not permit any delay time. For example, a coefficient kwhich depends on the degree of congestion in the cell of each terminal 2placed in the autonomous mode is provided for the amount of reduction inthe threshold value for switching.

When there is a terminal 2 in which a delay time of 20 ms is set as aQoS parameter and a terminal 2 in which a delay time of 80 ms is set asa QoS parameter, if the coefficient k=1, the amount of reduction in thethreshold value for switching of each terminal is given as follows:

The amount of reduction in the threshold value for the terminal 2 havinga delay time of 20 ms is given by the following equation:k·20/(20+80)=⅕=20%.

The amount of reduction in the threshold value for the terminal 2 havinga delay time of 80 ms is given by the following equation:k·80/(20+80)=⅘=80%.

When the shortage of the permissible margin in the scheduling mode ofthe base station which has been caused in order to secure thepermissible margin in the autonomous mode is relieved by lowering thethreshold values for switching of some terminals 2 placed in theautonomous mode, the radio resources management unit 66 sets theabove-mentioned coefficient k to 0 so as to maintain the currentthreshold values.

The radio resources management unit 66 further reduces the thresholdvalue to be set to each terminal 2 which has been determined as being aterminal which permits a delay time by the QoS parameter mapping unit 64in step ST7 c by a larger amount of reduction than that set in the caseof step ST10 c (in step ST11 c). Thus, the radio resources managementunit 66 sets a lowered threshold value for switching to each terminalwhich permits a delay time so that some of an excess number of terminalsplaced in the autonomous mode switch to the scheduling mode.

When, in step ST6 c, determining with the number of terminals placed inthe autonomous mode is appropriate, the radio resources management unit66 maintains the current threshold value set to each terminal (in stepST8 c).

On the other hand, when, in step ST6 c, determining with there are toofew terminals placed in the autonomous mode, the radio resourcesmanagement unit 66 raises the current threshold value for switching setto each terminal 2 (in step ST9 c).

The state in which the number of terminals placed in the autonomous modeis too small is the one in which a margin more than needed can beprovided with respect to the noise rise margin assigned to each terminal2 even if each terminal 2 performs data transmission at a data ratewhich is suited to the amount of transmission data thereof.

In this case, if the number of terminals staying in the cell and placedin the autonomous mode is made to increase by increasing the thresholdvalue, the noise rise margin assigned to each terminal 2 can be usedeffectively.

Thus, the radio resources management unit 66 determines the amount ofchange in the threshold value for switching based on the transmissiondata rate, the number of terminals placed in the autonomous mode, thenoise rise limit for the scheduling mode, and the amount of delay thatshould be permitted.

When determining the threshold value to be set to each terminal ineither of steps ST8 c to ST11 c, the radio resources management unit 66shifts to the process of step ST10 b of FIG. 19, generates a layer-3message including the changed threshold value, and transmits it to theabove-mentioned base station.

The base station which has received the message indicating the change inthe threshold value from the RNC 3, in step ST11 b of FIG. 19, transmitsthe above-mentioned information to each target terminal 2 which needs tochange its threshold value using the dedicated channel (DPCH) ifcommunications with each target terminal 2 via the dedicated channel(DPCH) are established, or transmits the above-mentioned information toeach target terminal 2 which needs to change its threshold value usingthe common channel (EACH) otherwise.

After that, each target mobile communication terminal 2 changes thethreshold value for switching of the transmission data buffer thereof byperforming the processes of steps ST12 b to ST14 b of FIG. 19.

The QoS parameter mapping unit 64, in step ST9 c, can determine whetheror not a delay time is permitted based on the QoS parameters, and theradio resources management unit 66 can change the amount of increase inthe threshold value for switching especially for each terminal 2 whichdoes not permit any delay time so that it is larger than that for eachterminal which permits a delay time based on the result of thedetermination. By doing in this way, the RNC can make each terminalswitch to the most appropriate transmission mode.

In each of steps ST9 c, ST10 c, and ST11 e, when the amount of increaseor decrease in the threshold value which is set at a time is too large,there is a possibility that a larger number of terminals 2 than neededchange their transmission modes. Therefore, it is desirable to make theamount of increase or decrease in the threshold value which is set at atime fall within a range of constant values in consideration of thenumber of terminals staying in the cell and placed in the autonomousmode, and so on, and to change the above-mentioned threshold value stepby step.

As mentioned above, according to the second method, since the RNC setsthe threshold value to each terminal 2 staying in the cell of each basestation individually, each terminal 2 is allowed to switch to acommunication mode which is suited to required communication conditions.Particularly, the mobile communication system can guarantee QoS set fordata communications between terminals 2 by making each terminal switchbetween the autonomous mode and the scheduling mode according to whetherdata handled by each terminal 2 permits a delay time.

In accordance with the first and second methods, the radio resourcesmanagement unit 66 of the RNC 3 determines the threshold for switchingbetween the communication modes for each terminal, as previouslyexplained. The present invention is not limited to this example.

For example, the base station can acquire QoS information etc. from theRNC 3, and the uplink-packet-communications management unit 24 of thebase station can determine the threshold for switching between thecommunication modes for each terminal.

The base station can further change the above-mentioned threshold valuedetermined by the RNC 3 according to traffic conditions at the currenttime etc., and can notify the changed threshold value to each terminal2. That is, the present invention includes a variant in which the basestation and the RNC 3 determine the above-mentioned threshold value incooperation with each other.

In this variant, the base station can be so constructed as to change thethreshold value notified thereto from the RNC 3 using theuplink-packet-communications management unit 24.

Next, the third method will be explained.

According to this third method, each terminal can be switched to themost appropriate transmission mode by transmitting information about achange in the threshold value for switching between the transmissionmodes to each terminal using a physical-layer signaling (i.e., an L1signaling). Furthermore, since the third method uses a higher-speedphysical layer signaling than that used by the second method, the thirdmethod can change the threshold value for switching according tovariations in the traffic of packets.

A physical-layer signaling (referred to as an L1 signaling from here on)is to assign information about the above-mentioned threshold to bitinformation about a physical layer disposed between each mobilecommunication terminal 2 and the base station, the bit information beingused to set up communication conditions of the physical layer.

For example, a new channel and its slot format are introduced, and aphysical-layer signaling is performed. The slot format specifies how toassign bits to one slot of transmission packet data.

In other words, the slot format defines a bit for setting of informationabout a change in the threshold value for switching in the transmissionpacket data in order to change the threshold value for switching usingthe physical-layer signaling.

As an example, UL-SICCH or the like is defined as the new channel forthe physical-layer signaling, and a bit to which a binary command forspecifying an increase or decrease in the threshold value for switchingis set is defined as the slot format.

As an alternative, a method using puncturing can be used. According tothis method, a portion of data which is assigned to the dedicatedchannel (DPCH) which is being used now is deleted, and informationspecifying the threshold value for switching is inserted into theportion. This method can be implemented by providing a powerful errorcorrection function for the original data so that a certain amount oferrors can be removed from the original data.

According to this method, since the bit error rate of the original dataincreases, a sufficiently-large number of bits cannot be assigned to thethreshold value for switching.

FIG. 21 is a diagram showing an example of a division of the noise risemargin of a base station according to embodiment 1 when the base stationdetermines the threshold for switching between the transmission modes ofeach terminal according to the third method. The basic conceptunderlying the third method will be explained with reference to thesefigures.

Assume that a plurality of mobile communication terminals 2 areaccommodated in the cell of a base station before the threshold forswitching between the transmission modes of each of the plurality ofterminals is changed. As shown in FIG. 21( a), the noise rise margin ofthe base station is divided into the permissible margin for the noiserise resulting from the autonomous mode, the permissible margin for thenoise rise resulting from the scheduling mode, and the permissiblemargin (another area shown in the figure and associated with thededicated channel, and so on) for the noise rise resulting fromtransmission via the dedicated channel, and so on.

In this case, the above-mentioned noise rise margin of the base stationis the permissible margin in which a margin associated with interferencewhich should be taken into consideration based on the operating statesof other cells and QoS is incorporated into the above-mentioned jammingmargin.

In general, packet communications can be easily carried outintermittently. In other words, in many cases the communication loadbecomes large when a large amount of data is uploaded, but thecommunication load decreases at the instant when the data transmissionstops.

When a large number of terminals 2 are staying in the cell and arehandling completely-different communication services, variations withtime in the traffic can be absorbed statistically to some extent.However, when a large number of terminals 2 staying in the cell arehandling the same communication service, variations with time in thetraffic can create a state of overload, or can make the traffic be toolight.

For example, when the frequency of packet communications by terminals 2placed in the scheduling mode increases (i.e., when packetcommunications by terminals 2 placed in the scheduling mode becomeactive), as shown in FIG. 21( b), the margin in the scheduling modewhich is included in the permissible margin of the base station must beincreased, and the margin in the autonomous mode is therefore reduced bythe increase in the margin in the scheduling mode.

On the contrary, when the frequency of packet communications byterminals placed in the scheduling mode decreases (i.e., when packetcommunications by terminals 2 placed in the scheduling mode becomeinactive), as shown in FIG. 21( c), it is desirable to decrease themargin in the scheduling mode among the permissible margin of the basestation, and to increase the margin in the autonomous mode by thedecrease in the margin in the scheduling mode.

As mentioned above, when decreasing the margin in the autonomous mode,what is necessary is just to make some terminals 2 switch from theautonomous mode to the scheduling mode. On the contrary, when increasingthe margin in the autonomous mode, what is necessary is just to makesome terminals switch from the scheduling mode to the autonomous mode.

It is necessary to change the threshold value for switching as quicklyas possible in order to carry out the above-mentioned switching betweenthe transmission modes while following the traffic in each of thetransmission modes which varies at a high speed. To this end, the thirdmethod uses the physical layer signaling having a higher speed thanlayer-3 messages.

FIG. 22 is a diagram showing a change sequence in a case of changing thethreshold of a transmission data buffer using the third method in themobile communication system according to embodiment 1. The uplink packettransmission management unit 24 of a target base station is informed ofa noise rise limit for uplink enhancements by the RNC 3 in advance (instep ST1 d).

To be more specific, the radio resources management unit 66 of the RNC 3determines the permissible margin of a fixed range for the target basestation in consideration of the QoS parameters managed by the QoSparameter mapping unit 64, the operating states of other cells otherthan that of the target base station, and the traffic conditions of thecell of the target base station, and notifies the determined permissiblemargin to the target base station.

The permissible margin notified to the target base station can bedivided into a margin in the scheduling mode and a margin in theautonomous mode, which are controllable margins as shown in FIG. 5, andmargins for noise rises resulting from the own cell interference, theother-cell interference, etc. which are uncontrollable margins as shownin FIG. 5.

The RNC 3 determines the above-mentioned whole permissible margin sothat it falls within a fixed range, and sets it to the base station. Onthe other hand, the uplink packet transmission management unit 24 of thebase station determines the rate of division of the whole permissiblemargin into the permissible margin in each of the transmission modes.

Then, the uplink packet transmission management unit 24 of the basestation receives a request for a transmission data rate in datatransmission in the scheduling mode from a terminal 2 staying in the owncell (in step ST2 d).

The uplink packet transmission management unit 24 determines thepermissible data rate in the autonomous mode, and also functions as ascheduler for managing data transmission in the scheduling mode. Thetransmission data rate from the above-mentioned terminal 2 isregistered, as a data transmission schedule in the scheduling mode, intothe uplink packet transmission management unit 24.

After that, the uplink packet transmission management unit 24 determineswhether or not the load conditions of the traffic in the scheduling modeis appropriate for the permissible margin assigned by the RNC 3, anddetermines the threshold value for switching so that the target terminalcan switch between the transmission modes according to thisdetermination result (in step ST3 d). This processing will be mentionedlater in detail with reference to FIG. 23.

When, in step ST3 d, determining the threshold value for switching, theuplink packet transmission management unit 24 notifies the changedthreshold value to the target terminal 2, which is instructed to changethe threshold, using the L1 signaling according to the sending operationmentioned above with reference to FIG. 10 (in step ST4 d).

There is a possibility that when the threshold changing command usingthe L1 signaling is a binary command for only increasing or decreasingthe threshold value, as mentioned above, the above-mentioned changingcommand is not correctly transmitted to the target terminal 2 because oftransmission errors etc.

For this reason, the base station continuously sends the L1-layercommand a plurality of number of times so that the changing command forchanging the threshold for switching can be surely transmitted to thetarget terminal 2 (in step ST5 d).

As mentioned above, according to the third method, processing carriedout through the RNC 3 in the process of changing the threshold value forswitching is reduced to a minimum. For this reason, communicationsbetween the base station and the RNC 3 can be omitted, and the changingof the threshold value for switching of each terminal 2 can be performedpromptly.

The process in step ST3 d of FIG. 22 of the mobile communication systemaccording to embodiment 1 will be explained in detail with reference tothe flow chart shown in FIG. 23.

First, the uplink packet transmission management unit 24 of the basestation checks conditions under which data transmission in thescheduling mode is scheduled within the own cell (in step ST1 e).

Then, the uplink packet transmission management unit 24 determineswhether or not the load on the traffic in the scheduling mode isappropriate with respect to the permissible margin assigned by the RNC 3based on the scheduling conditions checked in step ST1 e (in 59 step ST2e).

To be more specific, the uplink packet transmission management unit 24determines whether or not the load on the traffic in the scheduling modeis appropriate from both the number of terminals each of which hasnotified the base station that it is going to carry out datatransmission in the scheduling mode and the amount of data which shouldbe transmitted in the data communications.

For example, when a large number of terminals placed in the schedulingmode are staying within the own cell and there is a large amount of datawhich should be transmitted in data communications, and therefore thecommunication conditions (e.g., requirements on delay) specified by QoSabout data transmission in the scheduling mode are not satisfied, theuplink packet transmission management unit 24 determines that thereoccurs a state in which the load on the traffic in the scheduling modeis too large.

On the contrary, when a small number of terminals placed in thescheduling mode are staying within the own cell and there is a smallamount of data which should be transmitted, and the permissible marginin the scheduling mode is little used although the communicationconditions (e.g., requirements on delay) specified by QoS about datatransmission in the scheduling mode are fully satisfied, the uplinkpacket transmission management unit 24 determines that there occurs astate in which the load on the traffic in the scheduling mode is toosmall.

Only radio resources assigned to the uplink packet transmissionmanagement unit 24 are used in the scheduling mode, and an unlimitednumber of terminals 2 can be made to enter the scheduling mode if theassignment is repeated.

However, since data transmission is performed only in the orderaccording to the schedule when a large number of terminals 2 are made toenter the scheduling mode, a delay time occurs inevitably in datatransmission from each of them to the base station.

The above-mentioned determining method is the one of determining whetheror not the load on the traffic in the scheduling mode is appropriateaccording to how much delay time can be permitted for data which eachterminal 2 in the scheduling mode handles.

As another determining method other than the above-mentioned determiningmethod, there can be provided a process of focusing attention on theautonomous mode. To be more specific, the uplink packet transmissionmanagement unit 24 assumes a case where each terminal 2 staying withinthe own cell and placed in the autonomous mode carries out datatransmission at a maximum of a permissible data rate range notifiedthereto in advance, so as to estimate the noise rise.

The uplink packet transmission management unit then determines a statein which the permissible margin in the scheduling mode at the currenttime must be reduced after setting the permissible margin in theautonomous mode according to this noise rise, as the state in which theload on the traffic in the scheduling mode is too large.

On the other hand, the uplink packet transmission management unitdetermines a state in which the permissible margin in the schedulingmode at the current time can be increased even after setting thepermissible margin in the autonomous mode according to theabove-mentioned noise rise, as the state in which the load on thetraffic in the scheduling mode is too small.

In accordance with both the above-mentioned determining methods, it isdetermined that a state other than the above-mentioned state in whichthe load on the traffic in the scheduling mode is too large and theabove-mentioned state in which the load on the traffic in the schedulingmode is too small is the state in which the load on the traffic isappropriate.

When, in step ST2 e, determining that the load on the traffic isappropriate, the uplink packet transmission management unit 24 ends theprocessing shown in FIG. 23, and does not notify any information to eachterminal 2.

On the other hand, when, in step ST2 e, determining that the load on thetraffic is large, the uplink packet transmission management unit 24searches for a terminal 2 staying within the own cell and having a highfrequency of data transmission in the autonomous mode (in step ST3 e).For example, the uplink packet transmission management unit determines aterminal 2 which has provided notification of a permissible data rate inthe autonomous mode a number of times which exceeds a predeterminednumber of times to be the one having a high frequency of datatransmission in the autonomous mode.

The uplink packet transmission management unit 24 then determineswhether the terminal 2 which is determined to be the one having a highfrequency of data transmission in the autonomous mode in step ST3 epermits a delay time (in step ST4 e). The uplink packet transmissionmanagement unit carries out this determination based on the amount ofdelay specified by QoS about data which the terminal 2 in questionhandles. At this time, when determining that the terminal 2 in questiondoes not permit any delay, the uplink packet transmission managementunit 24 ends the processing shown in FIG. 23, and does not notify anyinformation to the terminal 2.

On the other hand, when determining that the terminal 2 permits a delaytime, the uplink packet transmission management unit 24 lowers thethreshold value for switching of the terminal 2 in question, and thenshifts to the process of step ST4 d of FIG. 22 (in step ST5 e).

When thus receiving a notification of the changed threshold value forswitching through the L1 signaling, the terminal 2 switches between thetransmission modes according to the threshold value and then answers thebase station that it has switched between the transmission modes.

The uplink packet transmission management unit 24 of the base stationdetermines whether the terminal 2 in question has switched to thescheduling mode by checking a response to the transmission mode changingcommand from the above-mentioned terminal 2 (in step ST6 e).

At this time, when determining that the terminal 2 has switched to thescheduling mode, the uplink packet transmission management unit 24estimates a new noise rise for the scheduling mode, and increases thenoise rise margin (i.e., the noise rise limit) in the scheduling modewithin the limit of the permissible margin set up by the RNC 3 (in stepST7 e).

On the other hand, when, in step ST6 e, determining that there is noresponse indicating that the terminal 2 has switched between thetransmission modes, and therefore the terminal 2 has not switched to thescheduling mode yet, the uplink packet transmission management unit 24shifts to the process of step ST5 d of FIG. 22, and continuouslytransmits the L1 signaling command in which the changed threshold valuefor switching is set up to the target terminal 2 (in step ST8 e). Afterthat, when receiving a response indicating that the terminal 2 hasswitched between the transmission modes, the uplink packet transmissionmanagement unit returns to the processing starting from step ST6 e.

When, in step ST2 e, determining that the load on the traffic in thescheduling mode is small, the uplink packet transmission management unit24 searches through all terminals 2 accommodated in the own cell foreither a terminal 2 having a low transmission frequency in thescheduling mode or a terminal 2 handling data which cannot permit anydelay time (in step ST9 e).

When, in step ST9 e, finding out either a terminal 2 having a lowtransmission frequency in the scheduling mode or a terminal 2 handlingdata which cannot permit any delay time, the uplink packet transmissionmanagement unit 24 raises the threshold value for switching of theterminal 2 in question, and shifts to the process of step ST4 d of FIG.22 (in step ST10 e).

As mentioned above, when receiving a notification of the changedthreshold value for switching through the L1 signaling, the terminal 2switches between the transmission modes according to the threshold valueand then answers the base station that it has switched between thetransmission modes.

The uplink packet transmission management unit 24 of the base stationdetermines whether the terminal 2 in question has switched to theautonomous mode by checking a response to the transmission mode changingcommand from the above-mentioned terminal 2 (in step ST11 e).

At this time, when determining that the terminal 2 has switched to theautonomous mode, the uplink packet transmission management unit 24estimates a new noise rise for the autonomous mode, and increases thenoise rise margin (i.e., the noise rise limit) in the autonomous modewithin the limit of the permissible margin set up by the RNC 3 (in stepST12 e).

On the other hand, when, in step ST11 e, determining that there is noresponse indicating that the terminal 2 has switched between thetransmission modes, and therefore the terminal 2 has not switched to theautonomous mode yet, the uplink packet transmission management unit 24shifts to the process of step ST5 d of FIG. 22, and continuouslytransmits the L1 signaling command in which the changed threshold valuefor switching is set up to the target terminal 2 (in step ST13 e). Afterthat, when receiving a response indicating that the terminal 2 hasswitched between the transmission modes, the uplink packet transmissionmanagement unit returns to the processing starting from step ST11 e.

As mentioned above, in accordance with the third method, since the basestation can notify information about a change in the threshold forswitching to each terminal 2 using a physical layer signaling having ahigher speed than that in the case of a layer-3 message, the thresholdfor switching can be changed according to variations in the traffic inpacket communications between the base station and each terminal 2.Furthermore, according to the third method, the whole noise rise margincan be divided appropriately into the permissible margins for the noiserises in the transmission modes according to the variations in thetraffic.

In accordance with the above-mentioned third method, the uplink packettransmission management unit 24 of the base station determines thethreshold for switching between the communication modes for eachterminal, as previously explained. The present invention is not limitedto this example.

For example, the radio resources management unit 66 of the RNC 3 can beso constructed as to determine the threshold for switching between thecommunication modes based on the QoS information grasped thereby and thetraffic conditions at the current time acquired from the base station.

In this case, the base station is notified of information specifying thethreshold for switching between the communication modes by the RNC 3,and then notifies it to the target terminal 2 according to the thirdmethod.

In the above-mentioned embodiment, the base station, including the RNC3, is so structured as to determine the threshold value for switching ofeach terminal 2, and each terminal 2 switches between the transmissionmodes according to the threshold value specified by the base station.However, the present invention is not limited to this structure.

For example, the base station, including the RNC 3, can be so structuredas to determine a transmission mode to which each terminal 2 shouldswitch based on the threshold value for switching, and each terminal 2can switch between the transmission modes according to a commandindicating the determined transmission mode from the base station.

Hereafter, examples in which the above-mentioned first through thirdmethods are applied to this variant, respectively, will be explained.

First, an operation in a case where the first method is applied to thevariant in which the base station determines a transmission mode towhich each terminal should switch, and each terminal 2 switches betweenthe transmission modes according to a command indicating the determinedtransmission mode from the base station will be explained in detail withreference to a flow chart shown in FIG. 24.

Since processes of steps ST1 a to ST8 a are the same as those of FIG.16, the explanation of them will be omitted hereafter. When, in eitherof steps ST6 a to ST8 a, determining the threshold value for switching,the resources management unit 66 of the RNC 3 notifies this thresholdvalue to the base station.

The uplink packet transmission management unit 24 of the base stationcompares the above-mentioned threshold value notified thereto from theRNC 3 with the amount of transmission data notified thereto in advancefrom each terminal 2 staying in the own cell, so as to determine thetransmission mode to be set to each terminal 2 (in step ST9 a).

For example, when the amount of transmission data notified thereto inadvance from each terminal exceeds the above-mentioned threshold value,the uplink packet transmission management unit determines that eachterminal should switch to the scheduling mode, whereas it determinesthat each terminal should switch to the autonomous mode otherwise.

When, in step ST9 a, determining the transmission mode to which eachterminal should switch, the uplink packet transmission management unit24 instructs the broadcast information transmission unit 28 to perform asignaling using broadcast information to inform each terminal 2 of thedetermined transmission mode (in step ST10 a).

To be more specific, in the process of step ST11 shown in FIG. 15, thebase station transmits the information specifying the transmission modedetermined thereby to each terminal, instead of information includingthe changed threshold value for switching.

Thus, the base station can know that each terminal 2 has switched towhich transmission mode by determining not only the threshold value forswitching but the transmission mode to which each terminal shouldswitch.

For this reason, the response signaling for notifying the transmissionmode to which each terminal 2 has switched to the base station, which isneeded when each terminal 2 has switched to the transmission modeaccording to the threshold value specified by the base station, can beomitted.

Next, an operation in a case where the second method is applied to thevariant in which the base station determines a transmission mode towhich each terminal should switch, and each terminal 2 switches betweenthe transmission modes according to a command indicating the determinedtransmission mode from the base station will be explained in detail withreference to a flow chart shown in FIG. 25.

Since processes of steps ST1 c to ST11 c are the same as those of FIG.20, the explanation of them will be omitted hereafter. When, in eitherof steps ST8 c, ST9 c, ST10 c, and ST11 c, determining the thresholdvalue for switching, the radio resources management unit 66 of the RNC 3notifies this determined threshold value to the base station.

The uplink packet transmission management unit 24 of the base stationcompares the above-mentioned threshold value notified thereto from theRNC 3 with the amount of transmission data notified thereto in advancefrom each terminal 2 which is determined to be the one which shouldswitch between the transmission modes, so as to determine thetransmission mode to be set to each terminal 2 in question (in step ST12c).

When, in step ST12 c, determining the transmission mode to which eachterminal in question should switch, the uplink packet transmissionmanagement unit 24 instructs either the downlink dedicated channeltransmission unit 29 or the downstream common channel transmission unit34 to perform a signaling using the dedicated channel or the commonchannel to inform each terminal 2 in question that each terminal 2 inquestion should switch to the determined transmission mode (in step ST13a).

To be more specific, in the process of step ST11 b shown in FIG. 19, thebase station transmits the information specifying the transmission modedetermined thereby to each terminal in question, instead of informationincluding the changed threshold value for switching. In this case, theprocesses of steps ST13 b and ST14 b shown in FIG. 19 are omitted.

Thus, the base station can know that each terminal 2 in question hasswitched to which transmission mode by determining not only thethreshold value for switching but the transmission mode to which eachterminal should switch.

For this reason, the response signaling for notifying the transmissionmode to which each terminal 2 has switched to the base station, which isneeded when each terminal 2 has switched to the transmission modeaccording to the threshold value specified by the base station, can beomitted.

In the above explanation, the radio resources management unit 66 of theRNC 3 determines the threshold for switching between the communicationmodes for each terminal. The present invention is not limited to thisexample.

For example, the base station can acquire QoS information etc. from theRNC 3, and the uplink-packet-communications management unit 24 of thebase station can determine the threshold for switching between thecommunication modes for each terminal.

By doing in this way, processing carried out through the RNC 3 in theprocess of determining the threshold value for switching between thecommunication modes can be reduced to a minimum, and the increase in thenumber of times which a signaling between the base station and the RNC 3is carried out can be reduced.

The base station can further change the above-mentioned threshold valuewhich is determined by the RNC 3 according to the traffic conditions atthe current time etc., and can compare the changed threshold value withthe amount of transmission data of each terminal 2 notified thereto inadvance, so as to determine the transmission mode to which each terminalshould to switch.

That is, the present invention includes a variant in which the basestation and the RNC 3 determine the above-mentioned threshold value incooperation with each other. In this variant, the base station can be soconstructed as to change the threshold value notified thereto from theRNC 3 using the uplink-packet-communications management unit 24.

Next, an operation in a case where the third method is applied to thevariant in which the base station determines the transmission mode towhich each terminal should switch, and each terminal 2 switches to thedetermined transmission mode according to a command indicating thedetermined transmission mode from the base station will be explained indetail with reference to a flow chart shown in FIG. 26.

Since processes of steps ST1 e to ST4 e are the same as those of FIG.23, the explanation of them will be omitted hereafter. When, in step ST4e, determining that the searched terminal 2 is a terminal which permitsa delay time, the uplink packet transmission management unit 24 lowersthe threshold value for switching of the terminal 2 in question (in stepST5 e-1).

Next, the uplink packet transmission management unit 24 compares thethreshold value determined in step ST5 e-1 with the amount oftransmission data notified thereto in advance from the terminal 2searched in step ST4 e, so as to determine the transmission mode whichthe terminal 2 in question should go into (in step ST5 e-2).

Then, the uplink packet transmission management unit 24 shifts to theprocess of step ST4 d of FIG. 22 after setting information specifyingthe transmission mode which should be set to the terminal 2 in questionto an L1 signaling command (in step ST5 e-3).

Since subsequent processes of steps ST6 e to ST8 e are the same as thoseof FIG. 23, the explanation of them will be omitted hereafter.

When, in step ST9 e, finding out either a terminal 2 having a lowtransmission frequency in the scheduling mode or a terminal 2 handlingdata which cannot permit any delay time, the uplink packet transmissionmanagement unit 24 raises the threshold value for switching of theterminal 2 in question (in step ST10 e-1).

Next, the uplink packet transmission management unit 24 compares thethreshold value determined in step ST10 e-1 with the amount oftransmission data notified thereto in advance from the terminal 2searched in step ST9 e, so as to determine the transmission mode whichshould be set to the terminal 2 in question (step ST10 e-2).

Then, the uplink packet transmission management unit 24 shifts to theprocess of step ST4 d of FIG. 22 after setting the informationspecifying the transmission mode which should be set to the terminal 2in question to an L1 signaling command mentioned above (in step ST10e-3).

Since subsequent processes of steps ST11 e to ST13 e are the same asthose of FIG. 23, the explanation of them will be omitted hereafter.

In accordance with the above-mentioned third method, the uplink packettransmission management unit 24 of the base station determines thethreshold for switching between the communication modes for eachterminal, as previously explained. The present invention is not limitedto this example.

For example, the radio resources management unit 66 of the RNC 3 can beso constructed as to determine the threshold for switching between thecommunication modes based on the QoS information grasped thereby and thetraffic conditions at the current time acquired from the base station.

In this case, the base station is notified of information specifying thethreshold for switching between the communication modes by the RNC 3,and then notifies it to the target terminal 2 according to the thirdmethod.

Furthermore, in the above-mentioned explanation, the uplink packettransmission management unit 24 of the base station determines thecommunication mode for each terminal, as previously explained. Thepresent invention is not limited to this example.

For example, the radio resources management unit 66 of the RNC 3 can beso constructed as to acquire the QoS information grasped thereby, theamount of transmission data which the terminal 2 in question is going totransmit, etc. by way of the base station, and to determine thetransmission mode which should be set to the terminal 2 in question.

In this case, in the processes of steps ST10 and ST11 shown in FIG. 15,and steps ST10 b and ST11 b shown in FIG. 19, the information specifyingthe transmission mode determined by the base station is transmitted tothe terminal in question, instead of the information including thechanged threshold value for switching.

After the transmission mode determined by the radio resources managementunit 66 is notified from RNC 3 to the base station, the base stationnotifies it to the terminal 2 in question using either of theabove-mentioned methods.

As mentioned above, according to this embodiment 1, each terminal 2 canbe placed in an appropriate transmission mode according to the operationconditions of the base station, and the permissible noise rise marginwhich is set to the base station can be appropriately divided into thepermissible margins in the transmission modes.

When setting the threshold for switching for each terminal 2, the mobilecommunication system enables determination of to which transmission modeeach terminal should switch in consideration of the QoS of data whicheach terminal 2 handles, and also enables efficient use of radioresources reflecting needs of data transmission of each terminal.

According to the above-mentioned embodiment, the mobile communicationsystem enables the base station to acquire transmission bufferinformation used for determining whether to make each terminal 2 switchbetween the transmission modes by allowing each terminal 2 to carry outa signaling to the base station, as previously explained.

If the frequency of the signaling of the transmission buffer informationto the base station by each terminal 2 cannot be changed according tothe maximum permissible delay of data which each terminal 2 handles, therequirements on delay cannot be satisfied even if the transmission modeis changed.

For example, when the frequency of the signaling of the transmissionbuffer information from each terminal 2 that arrives at the base stationis low, the base station cannot grasp the current state of thetransmission data buffer of each terminal 2 in time.

In this case, there is a possibility that the process of making eachtarget terminal 2 switch to either the scheduling mode or the autonomousmode is overdue, and, as a result, the requirements on delay in datacommunications by each terminal 2 in question are not satisfied.

Therefore, each mobile communication terminal 2 can change the frequencyof the signaling of transmission buffer information to the base stationaccording to the requirements on delay which are set for datacommunications handled thereby.

For example, in a case where each terminal 2 performs theabove-mentioned signaling to the base station at predeterminedintervals, terminals 2 which carry out data communications which mustsatisfy severe requirements on delay are made to perform theabove-mentioned signaling at short intervals, whereas terminals 2 whichcarry out data communications which only have to satisfy looserequirements on delay are made to perform the above-mentioned signalingat long intervals. The setup of the signaling intervals is performed foreach terminal according to the amount of permissible delay in datacommunications which each terminal is going to carry out.

Next, an explanation of the process of setting the above-mentionedsignaling intervals will be made. Counter information called SFN (SystemFrame Number) which is used as a reference of the transmission timing isset to P-CCPCH (BCH). The uplink packet transmission management unit 24of the base station determines the signaling intervals at which thesignaling of the transmission buffer information by each terminal 2 isperformed based on the QoS parameters and so on acquired from the RNC 3.

As methods of setting the signaling intervals to each terminal 2, thereare a first method of using broadcast information (setting the signalingintervals to each group of terminals 2 at a time), a second method ofusing the dedicated or common channel (individually setting thesignaling intervals to each terminal 2), and a third method of using aphysical-layer signaling, as in the case of performing theabove-mentioned signaling for changing the threshold for switching.

When receiving information about the above-mentioned signaling intervalsfrom the base station, each mobile communication terminal 2 demodulatesa signal set to each data channel using the back spreading demodulatingunit 46, as explained with reference to FIG. 11. The protocol processingunit 56 acquires the information about the above-mentioned signalingintervals from the signal which is demodulated by the back spreadingdemodulating unit 46.

The protocol processing unit 56 then sets the signaling intervalsacquired from the information about the above-mentioned signalingintervals to the buffer state transmission unit 55 as transmissionintervals for UL-SICCH at which each terminal notifies the state of thetransmission data buffer 58 to the base station. The mobilecommunication terminal 2 further synchronizes a timing at which it is totransmit data to the base station with a timing at which the basestation is to receive the data using an SFN value set to P-CCPCH (BCH).

A method of dividing terminals into groups can be used as the method ofsetting the above-mentioned signaling intervals efficiently. To be morespecific, terminals 2 which, for example, belong to QoS classes, such asa conversational-mode class and a streaming class, are divided intogroups according to maximum delay amounts which can be permitted in theQoS classes in question, and the above-mentioned signaling intervals aredetermined for each group.

On the other hand, signaling intervals longer than those set forterminals 2 which, for example, belong to the above-mentioned QoSclasses, such as the conversational-mode class and the streaming class,are set for terminals 2 belonging to QoS classes other than theabove-mentioned QoS classes. This method has an advantage of being ableto manage the amount of interference in each communication modeaccording to the QoS class to which terminals 2 included in each groupbelong.

Next, an application example of performing the signaling of theabove-mentioned transmission buffer information when the state of eachmobile communication terminal 2 satisfies predetermined conditions,instead of performing the signaling periodically as mentioned above,will be explained.

As the predetermined conditions, whether or not a certain amount oftransmission data is stored in the transmission data buffer 58 foruplink packet communications of each terminal 2 can be considered, and,when a certain amount of transmission data is stored in the transmissiondata buffer of each terminal 2, each terminal 2 performs the signalingof the above-mentioned transmission buffer information to the basestation.

In this case, the signaling of the above-mentioned transmission bufferinformation is not performed until a certain amount of transmission datais stored in the transmission data buffer 58. However, there are somecases where each terminal should perform the above-mentioned signalingwithout waiting until a certain amount of transmission data is stored inthe transmission data buffer 58 thereof, depending upon the type of datawhich each terminal 2 handles.

For example, although a response signal output from an application whicha terminal 2 executes via the Internet or the like has a small amount ofdata, the existence of the response signal should be notified to thebase station as soon as possible.

To this end, a timer for specifying the above-mentioned signalingintervals is set up for the terminal 2 so that, in a case of handlingdata which must satisfy severe requirements on delay, and the terminal 2performs the above-mentioned signaling when the timer reaches a fixedtime, without waiting until a certain amount of transmission data isstored in the transmission data buffer thereof.

The above-mentioned timer can be set up by performing a signalingspecifically using the structure of the base station, or can be set upby the terminal 2 itself.

First, an operation in the case of carrying out the signalingspecifically using the structure of the base station to set up theabove-mentioned timer will be explained with reference to FIGS. 10 and11. The uplink packet transmission management unit 51 of the terminal 2functions as the above-mentioned timer.

The RNC 3 generates timer information for specifying the signalingintervals dependent upon the QoS parameters using the QoS parametersabout data communications by a terminal 2 which is a target in which atimer is to be set up.

The base station then acquires the above-mentioned timer informationfrom the RNC 3, and transmits the timer information, as informationassociated with the dedicated channel, to the above-mentioned terminal 2via the downlink dedicated channel transmission unit 29.

In the above-mentioned terminal 2, the downlink dedicated channelreceiving unit 63 receives the above-mentioned information associatedwith the dedicated channel, and transmits the information to theprotocol processing unit 56. The protocol processing unit 56 reads thetimer information from the above-mentioned information associated withthe dedicated channel, and sends it to the uplink packet transmissionmanagement unit 51.

The uplink packet transmission management unit 51 sets up a timeraccording to the above-mentioned timer information, and, upon time-out,instructs the buffer state transmission unit 55 to execute a signalingof the above-mentioned transmission buffer information.

Next, a process of autonomously managing the timer of each terminal 2will be explained.

First, the uplink packet transmission management unit 51 determines atimer value based on the QoS information grasped thereby and whethertransmission of data has been carried out. When this timer expires, theuplink packet transmission management unit 51 instructs the buffer statetransmission unit 55 to carry out a signaling of the above-mentionedtransmission buffer information. As a method of specifying a timer whichenables efficient performance of the above-mentioned signaling, therecan be provided a method of setting up a timer in proportion to theamount of permissible delay in the conversational-mode class or thestreaming class by using, for example, the RNC 3 or the uplink packettransmission management unit 51.

In addition, for the interactive class or the background class, the RNC3 or the uplink packet transmission management unit 51 sets the timersof terminals 2 which have carried out communications for a shorter timethan that set to terminals 2 which carry out communications for thefirst time, and lengthens the set times of the timers of terminals stepby step as intervals at which communications are carried out becomelong.

By doing in this way, the RNC or the uplink packet transmissionmanagement unit 51 can flexibly set the number of times that thesignaling of the transmission data buffer information for the basestation is carried out according to demands on data communications. Forexample, the number of times that the above-mentioned signaling iscarried out can be efficiently controlled by lengthening the intervalsat which the signaling is carried out for terminals 2 which areperforming data communications with a low volume of traffic.

The above-mentioned method of carrying out a signaling periodically andthe above-mentioned method of using a timer can be used in combination.For example, terminals 2 which carries out data communications in whichthe amount of delay is severely set carries out a signaling of thetransmission data buffer information to the base station periodically,and terminals 2 which carries out data communications in which theamount of delay is loosely set carries out the above-mentioned signalingat intervals specified by a timer.

To be more specific, terminals 2 which handle data communicationsbelonging to the conversational-mode class or the streaming class setthe above-mentioned signaling intervals according to the maximumpermissible delay amount in the QoS class. On the other hand, terminals2 which handle data communications belonging to the interactive class orthe background class carry out the signaling according to a timer whichis set based on the QoS information grasped thereby and whethertransmission of data has been carried out.

By doing in this way, while the amount of interference of datacommunications by terminals 2 is managed by the base station, the numberof times that the signaling of the transmission data buffer informationis carried out by each terminal 2 can be controlled so as not toincrease more than desired. As a result, the signaling can beefficiently performed in the whole mobile communication system.

INDUSTRIAL APPLICABILITY

As mentioned above, the communication mode controlling method accordingto the present invention can be used for a mobile communicationterminal, such as a mobile phone which supports uplink packetcommunications, a base station and an RNC.

1. A method comprising: receiving a buffer status from a terminal, thebuffer status indicating an amount of data available for transmission;measuring, at a base station, signals to determine an amount of receivedpower; receiving, at the base station, from a radio network controlleran indication of a maximum received power; controlling scheduling forthe terminal in accordance with at least one of the indicated maximumreceived power or the buffer status; and transmitting an indication ofuplink radio resources to the terminal.
 2. The method of claim 1,wherein the determined amount of received power relates to interferencepower.
 3. The method of claim 1, wherein the indicated maximum receivedpower corresponds to a power that should not be exceeded as a result ofscheduling.
 4. The method of claim 1, wherein the buffer status isreceived at the base station.
 5. The method of claim 4, wherein the basestation is a Node-B implemented using wideband-code division multipleaccess (W-CDMA).
 6. The method of claim 1, further comprising: notifyingthe amount of received power to the radio network controller.
 7. Themethod of claim 1, further comprising: controlling scheduling inaccordance with a transmission power margin of the terminal.
 8. Themethod of claim 1, further comprising: receiving data from the terminal.9. The method of claim 8, further comprising: transmitting an ACK/NACKsignal to the terminal in response to the received data.
 10. The methodof claim 1, wherein the amount of data available for transmission is anamount of data stored in a terminal buffer.
 11. The method of claim 1,wherein controlling scheduling controls scheduling in accordance withthe indicated maximum received power.
 12. The method of claim 1, whereincontrolling scheduling controls scheduling in accordance with the bufferstatus.
 13. The method of claim 1, wherein controlling schedulingcontrols scheduling in accordance with the indicated maximum receivedpower and the buffer status.
 14. A method comprising: receiving a bufferstatus from a terminal, the buffer status indicating an amount of dataavailable for transmission; measuring, at a base station, signals todetermine an amount of received power; receiving, at the base station,from a radio network controller an indication of a maximum receivedpower; and causing control of terminal scheduling in accordance with theindicated maximum received power or the buffer status.
 15. The method ofclaim 14, where the causing control of terminal scheduling comprises:transmitting an indication of uplink radio resources to the terminal.16. A communications network configured to: receive a buffer status froma terminal, the buffer status indicating an amount of data available fortransmission; determine, at a base station, an amount of received power;receive, at the base station, from a radio network controller anindication of a maximum received power; control scheduling for theterminal in accordance with at least one of the indicated maximumreceived power or the buffer status; and transmit an indication ofuplink radio resources to the terminal.
 17. The communications networkof claim 16, wherein the determined amount of received power relates tointerference power.
 18. The communications network of claim 16, whereinthe indicated maximum received power corresponds to a power that shouldnot be exceeded as a result of scheduling.
 19. The communicationsnetwork of claim 16, wherein the buffer status is received at the basestation.
 20. The communications network of claim 19, wherein the basestation is a Node-B implemented using wideband-code division multipleaccess (W-CDMA).
 21. The communications network of claim 16, furtherconfigured to: notify the amount of received power to the radio networkcontroller.
 22. The communications network of claim 16, furtherconfigured to: control scheduling in accordance with a transmissionpower margin of the terminal.
 23. The communications network of claim16, further configured to: receive data from the terminal.
 24. Thecommunications network of claim 23, further configured to: transmit anACK/NACK signal to the terminal in response to the received data. 25.The communications network of claim 16, wherein the amount of dataavailable for transmission is an amount of data stored in a terminalbuffer.
 26. The communications network of claim 16, wherein schedulingis controlled in accordance with the indicated maximum received power.27. The communications network of claim 16, wherein scheduling iscontrolled in accordance with the buffer status.
 28. The communicationsnetwork of claim 16, wherein scheduling is controlled in accordance withthe indicated maximum received power and the buffer status.
 29. Acommunications network configured to: receive a buffer status from aterminal, the buffer status indicating an amount of data available fortransmission; measure, at a base station, signals to determine an amountof received power; receive, at the base station, from a radio networkcontroller an indication of a maximum received power; and cause controlof terminal scheduling in accordance with the indicated maximum receivedpower or the buffer status.
 30. The communications network of claim 29,further configured to: transmit an indication of uplink radio resourcesto the terminal.